1) The document discusses estimation theory and provides definitions of key terms like point estimate, interval estimate, unbiased estimator, relatively efficient estimator, and consistent estimator.
2) It also discusses properties of estimators like being biased or unbiased, and accurate or precise. The ideal is an unbiased estimator.
3) Methods for estimating the mean are presented for both large and small samples, including the formula for a confidence interval of the mean when the population standard deviation is known or unknown.
Makalah ini membahas tentang distribusi T-Student. Secara singkat, distribusi T-Student adalah distribusi probabilitas yang muncul ketika mengestimasi rata-rata populasi berdasarkan sampel kecil yang berasal dari populasi berdistribusi normal. Distribusi ini penting karena digunakan dalam pengujian hipotesis statistik ketika ukuran sampel kecil. Makalah ini menjelaskan pengertian, rumus, dan tabel distribusi T-Student beserta contoh soal aplikasinya.
Makalah ini membahas tentang distribusi T-Student. Secara singkat, distribusi T-Student adalah distribusi probabilitas yang muncul ketika mengestimasi rata-rata populasi berdasarkan sampel kecil yang berasal dari populasi berdistribusi normal. Distribusi ini penting karena digunakan dalam pengujian hipotesis statistik ketika ukuran sampel kecil. Makalah ini menjelaskan pengertian, rumus, dan tabel distribusi T-Student beserta contoh soal aplikasinya.
Dokumen tersebut membahas tentang uji statistika Chi-Square (X2) yang digunakan untuk menguji hipotesis beda proporsi lebih dari dua kelompok sampel, ketepatan distribusi frekuensi data, dan hubungan antar dua variabel. Metode analisisnya meliputi rumusan hipotesis nol dan alternatif, penentuan nilai kritis, perhitungan nilai X2 hitung, pengambilan keputusan menerima atau menolak hipotesis nol, dan penarikan
Dokumen ini membahas tentang kecukupan estimator dan kelas eksponensial. Definisi statistik cukup dan contohnya untuk distribusi eksponensial dan Bernoulli diberikan. Teorema-teorema seperti Rao-Blackwell dan Lehmann-Scheffe juga dibahas. Keluarga distribusi eksponensial reguler dijelaskan beserta statistik cukup lengkapnya.
Dokumen tersebut membahas berbagai ukuran penyebaran data, meliputi:
1. Definisi ukuran penyebaran data dan jenis-jenisnya seperti rentang, rentang antar kuartil, simpangan kuartil, rata-rata simpangan, simpangan baku, dan variansi.
2. Rumus-rumus perhitungan ukuran penyebaran termasuk rentang, rentang antar kuartil, dan simpangan kuartil.
3. Pengertian dan perhitungan variansi, deviasi stand
Dokumen tersebut membahas tentang distribusi normal dan aplikasinya. Distribusi normal merupakan distribusi probabilitas yang paling penting dalam statistika. Distribusi normal memiliki sifat-sifat seperti kurva yang simetris dan unimodal, serta sering muncul secara alami dalam fenomena alam. Distribusi normal digunakan untuk menganalisis data dan mengambil kesimpulan.
Dokumen tersebut membahas tentang probabilitas dan statistik, termasuk distribusi mean sampling, mean dan deviasi standar distribusi, probabilitas jarak antar dua pesawat terbang, persentase perusahaan yang mensyaratkan sertifikasi insinyur, serta estimasi mean dan deviasi standar populasi berdasarkan data sampling.
Module 7 Interval estimatorsMaster for Business Statistics.docxgilpinleeanna
Module 7
Interval estimators
Master for Business Statistics
Dane McGuckian
Topics
7.1 Interval Estimate of the Population Mean with a Known Population Standard Deviation
7.2 Sample Size Requirements for Estimating the Population Mean
7.3 Interval Estimate of the Population Mean with an Unknown Population Standard Deviation
7.4 Interval Estimate of the Population Proportion
7.5 Sample Size Requirements for Estimating the Population Proportion
7.1
Interval Estimate of the Population Mean with a Known Population Standard Deviation
Interval Estimators
Quantities like the sample mean and the sample standard deviation are called point estimators because they are single values derived from sample data that are used to estimate the value of an unknown population parameter.
The point estimators used in Statistics have some very desirable traits; however, they do not come with a measure of certainty.
In other words, there is no way to determine how close the population parameter is to a value of our point estimate. For this reason, the interval estimator was developed.
An interval estimator is a range of values derived from sample data that has a certain probability of containing the population parameter.
This probability is usually referred to as confidence, and it is the main advantage that interval estimators have over point estimators.
The confidence level for a confidence interval tells us the likelihood that a given interval will contain the target parameter we are trying to estimate.
The Meaning of “Confidence Level”
Interval estimates come with a level of confidence.
The level of confidence is specified by its confidence coefficient – it is the probability (relative frequency) that an interval estimator will enclose the target parameter when the estimator is used repeatedly a very large number of times.
The most common confidence levels are 99%, 98%, 95%, and 90%.
Example: A manufacturer takes a random sample of 40 computer chips from its production line to construct a 95% confidence interval to estimate the true average lifetime of the chip. If the manufacturer formed confidence intervals for every possible sample of 40 chips, 95% of those intervals would contain the population average.
The Meaning of “Confidence Level”
In the previous example, it is important to note that once the manufacturer has constructed a 95% confidence interval, it is no longer acceptable to state that there is a 95% chance that the interval contains the true average lifetime of the computer chip.
Prior to constructing the interval, there was a 95% chance that the random interval limits would contain the true average, but once the process of collecting the sample and constructing the interval is complete, the resulting interval either does or does not contain the true average.
Thus there is a probability of 1 or 0 that the true average is contained within the interval, not a 0.95 probability.
The interval limits are random variables because the ...
This document discusses point and interval estimation. It defines an estimator as a function used to infer an unknown population parameter based on sample data. Point estimation provides a single value, while interval estimation provides a range of values with a certain confidence level, such as 95%. Common point estimators include the sample mean and proportion. Interval estimators account for variability in samples and provide more information than point estimators. The document provides examples of how to construct confidence intervals using point estimates, confidence levels, and standard errors or deviations.
Dokumen tersebut membahas tentang uji statistika Chi-Square (X2) yang digunakan untuk menguji hipotesis beda proporsi lebih dari dua kelompok sampel, ketepatan distribusi frekuensi data, dan hubungan antar dua variabel. Metode analisisnya meliputi rumusan hipotesis nol dan alternatif, penentuan nilai kritis, perhitungan nilai X2 hitung, pengambilan keputusan menerima atau menolak hipotesis nol, dan penarikan
Dokumen ini membahas tentang kecukupan estimator dan kelas eksponensial. Definisi statistik cukup dan contohnya untuk distribusi eksponensial dan Bernoulli diberikan. Teorema-teorema seperti Rao-Blackwell dan Lehmann-Scheffe juga dibahas. Keluarga distribusi eksponensial reguler dijelaskan beserta statistik cukup lengkapnya.
Dokumen tersebut membahas berbagai ukuran penyebaran data, meliputi:
1. Definisi ukuran penyebaran data dan jenis-jenisnya seperti rentang, rentang antar kuartil, simpangan kuartil, rata-rata simpangan, simpangan baku, dan variansi.
2. Rumus-rumus perhitungan ukuran penyebaran termasuk rentang, rentang antar kuartil, dan simpangan kuartil.
3. Pengertian dan perhitungan variansi, deviasi stand
Dokumen tersebut membahas tentang distribusi normal dan aplikasinya. Distribusi normal merupakan distribusi probabilitas yang paling penting dalam statistika. Distribusi normal memiliki sifat-sifat seperti kurva yang simetris dan unimodal, serta sering muncul secara alami dalam fenomena alam. Distribusi normal digunakan untuk menganalisis data dan mengambil kesimpulan.
Dokumen tersebut membahas tentang probabilitas dan statistik, termasuk distribusi mean sampling, mean dan deviasi standar distribusi, probabilitas jarak antar dua pesawat terbang, persentase perusahaan yang mensyaratkan sertifikasi insinyur, serta estimasi mean dan deviasi standar populasi berdasarkan data sampling.
Module 7 Interval estimatorsMaster for Business Statistics.docxgilpinleeanna
Module 7
Interval estimators
Master for Business Statistics
Dane McGuckian
Topics
7.1 Interval Estimate of the Population Mean with a Known Population Standard Deviation
7.2 Sample Size Requirements for Estimating the Population Mean
7.3 Interval Estimate of the Population Mean with an Unknown Population Standard Deviation
7.4 Interval Estimate of the Population Proportion
7.5 Sample Size Requirements for Estimating the Population Proportion
7.1
Interval Estimate of the Population Mean with a Known Population Standard Deviation
Interval Estimators
Quantities like the sample mean and the sample standard deviation are called point estimators because they are single values derived from sample data that are used to estimate the value of an unknown population parameter.
The point estimators used in Statistics have some very desirable traits; however, they do not come with a measure of certainty.
In other words, there is no way to determine how close the population parameter is to a value of our point estimate. For this reason, the interval estimator was developed.
An interval estimator is a range of values derived from sample data that has a certain probability of containing the population parameter.
This probability is usually referred to as confidence, and it is the main advantage that interval estimators have over point estimators.
The confidence level for a confidence interval tells us the likelihood that a given interval will contain the target parameter we are trying to estimate.
The Meaning of “Confidence Level”
Interval estimates come with a level of confidence.
The level of confidence is specified by its confidence coefficient – it is the probability (relative frequency) that an interval estimator will enclose the target parameter when the estimator is used repeatedly a very large number of times.
The most common confidence levels are 99%, 98%, 95%, and 90%.
Example: A manufacturer takes a random sample of 40 computer chips from its production line to construct a 95% confidence interval to estimate the true average lifetime of the chip. If the manufacturer formed confidence intervals for every possible sample of 40 chips, 95% of those intervals would contain the population average.
The Meaning of “Confidence Level”
In the previous example, it is important to note that once the manufacturer has constructed a 95% confidence interval, it is no longer acceptable to state that there is a 95% chance that the interval contains the true average lifetime of the computer chip.
Prior to constructing the interval, there was a 95% chance that the random interval limits would contain the true average, but once the process of collecting the sample and constructing the interval is complete, the resulting interval either does or does not contain the true average.
Thus there is a probability of 1 or 0 that the true average is contained within the interval, not a 0.95 probability.
The interval limits are random variables because the ...
This document discusses point and interval estimation. It defines an estimator as a function used to infer an unknown population parameter based on sample data. Point estimation provides a single value, while interval estimation provides a range of values with a certain confidence level, such as 95%. Common point estimators include the sample mean and proportion. Interval estimators account for variability in samples and provide more information than point estimators. The document provides examples of how to construct confidence intervals using point estimates, confidence levels, and standard errors or deviations.
The document discusses estimation and different types of estimates used to estimate population parameters based on sample data. Point estimates provide a single value while interval estimates provide a range of values. Good estimators are unbiased, efficient, and consistent. Common point estimators are the sample mean and sample standard deviation. Interval estimates use the point estimate plus/minus a margin of error calculated from the standard error. Confidence intervals provide a probability that the population parameter lies within the interval estimate.
Chapter 7 – Confidence Intervals And Sample SizeRose Jenkins
This document discusses confidence intervals for means and proportions. It defines key terms like point estimates, interval estimates, confidence levels, and confidence intervals. It provides formulas for calculating confidence intervals for means when the population standard deviation is known or unknown, and when the sample size is greater than or less than 30. Formulas are also given for calculating confidence intervals for proportions, and for determining the minimum sample size needed for estimating means and proportions within a desired level of accuracy. Examples of applying these concepts to sample data are also included.
Chapter 7 – Confidence Intervals And Sample Sizeguest3720ca
This document discusses confidence intervals for means and proportions. It defines key terms like point estimates, interval estimates, confidence levels, and confidence intervals. It provides formulas for calculating confidence intervals for means when the population standard deviation is known or unknown, and when the sample size is greater than or less than 30. Formulas are also given for calculating confidence intervals for proportions, and for determining the minimum sample size needed for estimating means and proportions within a desired level of accuracy. Examples of applying these concepts to sample data are also included.
This document discusses statistical confidence interval estimation. It covers:
1) Confidence interval estimation for the mean when the population standard deviation is known and unknown.
2) Confidence interval estimation for the proportion.
3) Factors that affect confidence interval width like data variation, sample size, and confidence level.
4) How to estimate sample sizes needed to estimate a population mean or proportion within a given level of precision and confidence.
This document discusses various methods for constructing confidence intervals to estimate population parameters using sample statistics. It covers confidence interval estimation for the mean when the population standard deviation is known and unknown, estimation for the proportion, and addresses situations involving finite populations. Factors that influence confidence interval width and formulas for determining necessary sample sizes are also presented. Examples are provided to illustrate how to set up confidence intervals and calculate required sample sizes.
This document discusses confidence intervals and margin of error in statistical analysis. It defines key terminology like population mean, sample mean, standard deviation, and standard error. It explains that the margin of error depends on the sample size and standard deviation, and provides the formula for calculating sample size needed to achieve a given margin of error. Several examples are provided to illustrate how to construct confidence intervals and determine required sample sizes.
The statistical Confidence Level (C.L.) is the probability that the corresponding confidence interval covers the true ( but unknown ) value of a population parameter. Such confidence interval is often used as a measure of uncertainty about estimates of population parameters
This document discusses various topics related to report writing including findings, conclusions, recommendations, types of reports, report sections, and explores common myths about reports. It provides examples of different sections within reports including an executive summary, company overview, factors for analysis and methodology. The summaries focus on conveying the high-level purpose or content of the different sections while keeping the summary brief.
This document provides an overview of statistical confidence intervals. It defines key terms like point estimates, confidence levels, and confidence intervals. The document explains how to calculate confidence intervals for a population mean when the population standard deviation is known, using a point estimate, standard error, and critical z-value. It emphasizes that a confidence interval provides more information than a point estimate alone by indicating the range of uncertainty around the estimated value. Examples are given to demonstrate how to interpret a 95% confidence interval.
Estimating population values ppt @ bec domsBabasab Patil
This document discusses confidence intervals for estimating population parameters. It covers confidence intervals for the mean when the population standard deviation is known and unknown, as well as confidence intervals for the population proportion. Key points include:
- A confidence interval provides a range of plausible values for an unknown population parameter based on a sample statistic.
- The margin of error and confidence level affect the width of a confidence interval.
- The t-distribution is used instead of the normal when the population standard deviation is unknown.
- Sample size formulas allow determining the required sample size to estimate a population parameter within a specified margin of error and confidence level.
This document outlines key concepts related to estimation and confidence intervals. It defines point estimates as single values used to estimate population parameters and interval estimates as ranges of values within which the population parameter is expected to occur. Confidence intervals provide an interval range based on sample observations within which the population parameter is expected to fall at a specified confidence level, such as 95% or 99%. The document discusses how to construct confidence intervals for the population mean when the population standard deviation is known or unknown.
The document discusses key concepts related to sampling methods in marketing research. It defines sampling elements, population, sampling frame, and sampling unit. It presents formulas for calculating sample size when estimating means of continuous variables and proportions. The formula for means involves variables like confidence level (Z), standard deviation (s), and tolerable error (e). The formula for proportions uses variables like confidence level (Z), estimated proportion (p), and tolerable error (e). The document provides an example of each formula and discusses limitations of the formulas related to number of centers, multiple questions, and cell size in analysis.
This document discusses determining sample size for statistical analysis. It provides formulas for calculating the minimum sample size needed when estimating a population mean or proportion. For a population mean, the formula is: n = (za/2σ/E)2, where z is the confidence level, σ is the population standard deviation, and E is the desired level of accuracy or margin of error. For a population proportion, the formula is: n = pq(za/2/E)2, where p is the population proportion and q is 1-p. The document provides examples of using these formulas to determine the required sample size for different studies based on the confidence level, population characteristics, and margin of error. It also discusses rounding
This document provides an overview of lectures for a business statistics course covering weeks 43-50. It discusses key concepts in estimation including:
- Point and interval estimators for population parameters based on sample statistics
- Properties of unbiased and consistent estimators
- How to construct confidence intervals for estimating the population mean when the standard deviation is known, including interpreting the results.
- How sample size affects the width of confidence intervals and precision of estimates.
This document discusses confidence intervals and how they can be used to estimate population parameters from sample data. It provides the following key points:
- Confidence intervals provide a range of values that is likely to include an unknown population parameter, unlike a point estimate which is a single value. They indicate the reliability of an estimate.
- The formula for a confidence interval of a population mean takes the sample mean and adds/subtracts a critical value times the standard error.
- When the population standard deviation is unknown, the student's t-distribution must be used instead of the normal distribution, as it accounts for the extra uncertainty of estimating the standard deviation from a sample.
- Sample size calculations can determine the
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Standard error values represent the variability in a student's score if they were to take a test multiple times. The methodology used to develop the SFA provides a standard error value for each possible score. Confidence intervals can be constructed around each score by subtracting and adding 1.96 times the standard error from the criterion score. This provides a 95% confidence interval of a student's true score. The document provides examples of how to calculate confidence intervals for two students' scores.
Similar to Estimasi Parameter (Teori Estimasi) (20)
How to Add Chatter in the odoo 17 ERP ModuleCeline George
In Odoo, the chatter is like a chat tool that helps you work together on records. You can leave notes and track things, making it easier to talk with your team and partners. Inside chatter, all communication history, activity, and changes will be displayed.
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Date: May 29, 2024
Tags: Information Security, ISO/IEC 27001, ISO/IEC 42001, Artificial Intelligence, GDPR
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Executive Directors Chat Leveraging AI for Diversity, Equity, and InclusionTechSoup
Let’s explore the intersection of technology and equity in the final session of our DEI series. Discover how AI tools, like ChatGPT, can be used to support and enhance your nonprofit's DEI initiatives. Participants will gain insights into practical AI applications and get tips for leveraging technology to advance their DEI goals.
বাংলাদেশের অর্থনৈতিক সমীক্ষা ২০২৪ [Bangladesh Economic Review 2024 Bangla.pdf] কম্পিউটার , ট্যাব ও স্মার্ট ফোন ভার্সন সহ সম্পূর্ণ বাংলা ই-বুক বা pdf বই " সুচিপত্র ...বুকমার্ক মেনু 🔖 ও হাইপার লিংক মেনু 📝👆 যুক্ত ..
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it describes the bony anatomy including the femoral head , acetabulum, labrum . also discusses the capsule , ligaments . muscle that act on the hip joint and the range of motion are outlined. factors affecting hip joint stability and weight transmission through the joint are summarized.
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A workshop hosted by the South African Journal of Science aimed at postgraduate students and early career researchers with little or no experience in writing and publishing journal articles.
A review of the growth of the Israel Genealogy Research Association Database Collection for the last 12 months. Our collection is now passed the 3 million mark and still growing. See which archives have contributed the most. See the different types of records we have, and which years have had records added. You can also see what we have for the future.
RPMS TEMPLATE FOR SCHOOL YEAR 2023-2024 FOR TEACHER 1 TO TEACHER 3
Estimasi Parameter (Teori Estimasi)
1. BAB 4 (bag. 1)
Teori Estimasi
1
4.1 Pengertian dan
Sifat-Sifat Estimator
4.2 Estimasi Rataan
4.3 Estimasi Proporsi
2. 4.1 Pengertian dan Sifat-sifat
Estimator
a. Pengertian Estimasi (penaksiran/pendugaan)
Menurut Bluman (2009, p.356):
Estimasi merupakan proses menaksir nilai sebuah parameter berdasarkan
informasi yang diperoleh dari sebuah sampel.
Misalnya hasil suatu survey menyatakan estimasi sbb:
• Rataan pengeluaran pulsa/bulan mahasiswa di Bandung pada tahun 2015 sebesar
Rp. 50.270,-
• Lima belas persen profesi orang tua mahasiswa di Tel-U adalah PNS, dsb.
• Rataan harga mobil bekas 1500 cc tahun 2010 antara Rp. 100 juta sd.Rp. 200
juta.
3. Macam Estimasi Statistik
Suatu parameter dapat diestimasi melalui 2 macam
penaksiran statistik , yaitu :
1. Menaksir dengan sebuah nilai statistik dikenal dengan
istilah point estimate
2. Menaksir dengan selang nilai statistik dikenal dengan
istilah interval estimate
θ̂
2
1 θ̂
θ
θ̂
θ̂
@copyright axy_2015
4. Sifat-Sifat Estimator
1. Unbias Estimator
Jika statistik sampel sama dengan parameter
populasi (AKURAT).
2. Relatively Efficient Estimator
Unbias estimator yang memiliki variansi terkecil
(PRESISI).
3. Consistent Estimator
Unbias estimator yang mendekati nilai yang
sebenarnya sejalan dengan bertambahnya ukuran
sampel.
b. Sifat-sifat Estimator
5. Penaksiran yang BIAS
(BIASED)
Hasil penaksiran yang terlalu tinggi atau
terlalu rendah dari yang sebenarnya .
Apa yang menjadi persoalan
dalam estimasi?
Penaksiran yang IDEAL
(UBIASED)
Jika nilai suatu penaksiran sama dengan
nilai yang sebenarnya .
Seperti apa penaksiran yang
dikehendaki?
θ̂
θ̂
biased unbiased
1. Unbiased Estimator
9. 3. Consistent Estimator
Unbias estimator yang mendekati nilai yang sebenarnya sejalan dengan
bertambahnya ukuran sampel. Pertanyaan penting dalam estimasi adalah
berapa besar ukuran sampel yang harus ditetapkan agar menciptakan
suatu estimasi yang akurat. Salah satu faktor yang menentukan ukuran
sampel adalah standar deviasi, oleh karena itu semakin besar ukuran
sampelnya menyebabkan variansi semakin kecil dan konsekuensinya
menciptakan unbias estimator yang lebih baik.
X
µ
n =50
n =15
n =5
terbaik
10. • Interval estimate (estimasi interval) adalah selang/interval/rentang nilai
suatu statistik yang digunakan untuk menaksir suatu parameter
• Confidence interval (interval kepercayaan) adalah kemungkinan estimasi
interval akan mengandung parameter yang berasal dari pemilihan
sejumlah sampel yang besar.
• Confidence level/degree of confidence (tingkat kepercayaan) adalah
suatu nilai kepercayaan yang ekivalen dengan nilai desimal (1–α) atau
persentasi (1–α)100%.
• Notasi α dikenal level of significence sebagai nilai dari tingkat
kesalahan/taraf nyata yang dapat dikatakan sebagai kemungkinan nilai
suatu estimasi parameter berada di luar batas kiri atau kanan α/2.
Istilah dalam Estimasi
Suatu interval kepercayaan selalu menetapkan tingkat kepercayaan biasanya dengan
90%, 95%, atau 99%, yang merupakan ukuran dari keandalan (reliability) prosedur.
Semakin besar kepercayaan maka semakin lebar interval parameternya.
13. 4.2 Estimasi Rataan
Misalkan suatu populasi berdistribusi normal memiliki parameter
rataan µ dan standar deviasi . Dengan asumsi bahwa diketahui
maka nilai µ yang tidak diketahui akan ditaksir.
Penaksiran rataan dari satu populasi meliputi taksiran rataan:
• Sampel besar dan
• Sampel kecil
14. Interval Kepercayaan Rataan
dengan Simpangan baku DIKETAHUI
Jika 𝑥 rataan sampel acak berukuran n dari suatu populasi berdistribusi
normal dengan variasi σ2
yang diketahui, maka untuk α yang spesifik rumus
untuk taksiran interval kepercayaan sebesar (1-α)100% untuk (confidence
interval of the mean) adalah:
Dimana zα/2 adalah nilai sebaran normal
menghasilkan luas α/2 di sebelah kanan
dan kirinya. Menggunakan tabel normal
dapat dicari nilai dari zα/2 yang
ditentukan oleh tingkat kepercayaaan.
1 ̶ a
z
a/2
-za/2
a/2
za/2
𝑥−𝑧𝛼 2
𝜎
𝑛
< 𝜇 < 𝑥 + 𝑧𝛼 2
𝜎
𝑛
4.2 Estimasi Rataan
a. Estimasi Rataan Sampel Besar
15. Margin Error dan Ukuran Sampel (n) Minimal
Formulasi ukuran sampel untuk taksiran rataan populasi diperoleh dari
formulasi margin error-nya :
𝐸 = 𝑍∝/2
𝜎
𝑛
Formulasi ukuran sampel minimum untuk taksiran interval rataan populasi
sebagai berikut (Walpole, 2012):
Jika 𝑥 digunakan untuk menaksir µ, kita dapat percaya (1-α)100% bahwa
kekeliruannya akan kurang dari nilai “e” tertentu jika jumlah sampelnya adalah:
𝑛 =
𝑍𝛼/2. 𝜎
𝐸
2
Teorema ini dapat diterapkan jika variansi populasi diketahui, atau tersedia
n ≥ 30 untuk melakukan taksiran variansi tersebut.
Margin of Error :
Tingkat kesalahan maksimum penaksir
16. 𝑍𝛼/2. 𝜎
𝐸
2
Memperhatikan formulasi ini dapat dirinci 3 hal yang mempengaruhi ukuran
sampel (n), yaitu :
1. Tingkat kesalahan atau kesalahan maksimum yang diijinkan
2. Standar deviasi populasi
3. Tingkat kepercayaan
Ringkasan nilai zα/2 untuk suatu (1–α)100% tertentu:
• untuk suatu interval kepercayaan 90%, maka zα/2 =z0.05=1.65
• untuk suatu interval kepercayaan 95%, maka zα/2 =z0.025=1.96
• untuk suatu interval kepercayaan 99%, maka zα/2 =z0.005=2.58
17. b. Estimasi Rataan Sampel Kecil
Selang Kepercayaan Rataan
dengan Simpangan baku TIDAK DIKETAHUI
Jika 𝑥 dan s adalah rataan dan simpangan baku sampel berukuran n < 30 dari suatu
populasi yang terdistribusi mendekati normal, maka selang kepercayaan
(1 – α)100% untuk rataan µ adalah:
Dimana 𝑡∝ 2 adalah nilai distribusi-t
dengan derajat kebebasan sebesar
v=n-1 menghasilkan luas α/2 di
sebelah kanan dan kirinya.
1 ̶ a
t
a/2
-ta/2
a/2
ta/2
𝑥 − 𝑡∝ 2
𝑠
𝑛
< 𝜇 < 𝑥 + 𝑡∝ 2
𝑠
𝑛
18. Latihan 1
Manajer Marketing sebuah dealer otomotif ingin memperkirakan berapa lama waktu yang dibutuhkan
untuk menjual suatu jenis mobil. Hasil sampling 50 mobil memiliki rataan waktu 54 hari dan
diasumsikan standar deviasi populasi 6 hari, maka:
Pertanyaan:
a. Tentukan taksiran interval kepercayaan 95% dari rataan waktu terjualnya suatu jenis mobil dari
populasi yang sebenarnya?
Solusi:
a. Dengan taksiran titik rataan populasi sebesar 54 hari yang diperoleh dari rataan sampelnya, maka
taksiran interval kepercayaan 95% menggunakan nilai zα/2 = z0.025=1.96 diperoleh :
𝑥−𝑧𝛼 2
𝜎
𝑛
< 𝜇 < 𝑥 + 𝑧𝛼 2
𝜎
𝑛
54 − 1.96
6
50
< 𝜇 < 54 + 1.96
6
50
54 − 1.7 < 𝜇 < 54 + 1.7
52.3 < 𝜇 < 55.7 𝑎𝑡𝑎𝑢 54 1.7∗
*) Nilai margin error 1.7 merupakan
pembulatan 1 digit desimal dari 1.663.
Kesimpulan: Dengan kepercayaan
95% diperoleh taksiran rataan waktu
terjualnya suatu jenis mobil dari
populasi yang sebenarnya dengan
interval antara 52.3 dan 55.7 hari dari
sampling sebanyak 50 mobil.
19. Latihan 1 (lanjutan)
Manajer Marketing sebuah dealer otomotif ingin memperkirakan berapa lama waktu yang dibutuhkan
untuk menjual suatu jenis mobil. Hasil sampling 50 mobil memiliki rataan waktu 54 hari dan
diasumsikan standar deviasi populasi 6 hari, maka:
Pertanyaan:
b. Apabila margin error yang diinginkan kurang dari 0.05, berapa ukuran sampel minimalnya?
Solusi:
b. Penyelesaian di atas diperoleh untuk
margin error 1.7 hari dengan ukuran
sampel 50. Apabila margin error yang
diharapkan kurang dari 1 hari, maka
ukuran sampel minimalnya adalah:
Kesimpulan: Apabila margin error yang diharapkan kurang dari 1 hari, maka ukuran sampel
minimalnya 139 mobil. Semakin kecil margin of error maka ukuran sampel minimalnya bertambah
dari 54 menjadi 139 mobil.
20. Latihan 2
Pada persoalan latihan 5.1, misalnya ukuran sampelnya adalah 25 dengan rataan
waktu 54 hari dan standar deviasi sampelnya adalah 5 hari berasal dari populasi
berdistribusi hampiran normal, maka:
Pertanyaan:
Tentukan taksiran interval kepercayaan 95% dari rataan populasinya?
Solusi:
Persoalan taksiran sampel kecil 25<30, dengan standar deviasi sampel diketahui 5 hari yang
berasal dari populasi berdistribusi hampiran normal; dan karena standar deviasi
populasinya tidak diketahui, maka disubstitusi dari standar deviasi sampel s = 5 hari,
sehingga berlaku formulasi taksiran interval kepercayaan 95% untuk sampel kecil sebagai
berkut:
Dengan taksiran titik rataan populasi sebesar 54
hari yang diperoleh dari rataan sampelnya,
maka taksiran interval kepercayaan 95%
menggunakan nilai tα/2 = t0.025 dengan v = n–
1=25–1=24 atau ditulis sebagai t0.025;24 = 2.064
diperoleh :
*) Nilai margin error 2.1 merupakan pembulatan 1 digit
desimal dari 2.064.
𝑥−𝑡𝛼 2
𝑠
𝑛
< 𝜇 < 𝑥 + 𝑡𝛼 2
𝑠
𝑛
54 − 2.064
5
25
< 𝜇 < 54 + 2.064
5
25
54 − 2.1 < 𝜇 < 54 + 2.1
51.9 < 𝜇 < 56.1 𝑎𝑡𝑎𝑢 54 2.1∗
21. Latihan 2 (lanjutan)
Kesimpulan: Dengan kepercayaan 95%
diperoleh taksiran rataan waktu
terjualnya suatu jenis mobil dari populasi
yang sebenarnya dengan interval antara
51.9 dan 56.1 hari dari sampling
sebanyak 25 mobil.
𝑥−𝑡𝛼 2
𝑠
𝑛
< 𝜇 < 𝑥 + 𝑡𝛼 2
𝑠
𝑛
54 − 2.064
5
25
< 𝜇 < 54 + 2.064
5
25
54 − 2.1 < 𝜇 < 54 + 2.1
51.9 < 𝜇 < 56.1 𝑎𝑡𝑎𝑢 54 2.1∗
*) Nilai margin error 2.1 merupakan pembulatan 1
digit desimal dari 2.064.
22. c. Estimasi Selisih Rataan Sampel Kecil
Taksiran selisih rataan adalah penaksiran selisih rataan (μ1–μ2) yang berasal
dari 2 buah populasi.
Ada 3 persoalan dalam interval taksiran selisih rataan μ1 – μ2 :
1. Kasus pertama, jika simpangan baku 1 dan 2 DIKETAHUI.
2. Kasus kedua, jika simpangan baku 1 dan 2 TIDAK DIKETAHUI
tetapi 1=2
3. Kasus ketiga, jika simpangan baku 1 dan 2 TIDAK DIKETAHUI
tetapi 1=2
23. Pertama:
Interval taksiran selisih rataan μ1 – μ2
jika simpangan baku 1 dan 2 DIKETAHUI.
Jika 𝑥1 dan 𝑥2 masing-masing adalah rataan sampel acak berukuran n1 dan n2
yang diambil dari populasi yang simpangan bakunya diketahui 1 dan 2, maka
selang kepercayaan (1 – a)100% untuk μ1 – μ2 diberikan oleh:
2
2
2
1
2
1
2
/
2
1
2
1
2
2
2
1
2
1
2
/
2
1 )
(
)
(
n
n
Z
x
x
n
n
Z
x
x
a
a
24. Kedua:
Interval taksiran selisih rataan μ1 – μ2
jika simpangan baku 1 dan 2TIDAK DIKETAHUI
tetapi 1=2
Jika 𝑥1 dan 𝑥2 masing-masing adalah rataan sampel acak berukuran n1 dan n2
yang bebas berasal dari 2 populasi yang hampir normal dengan simpangan
bakunya TIDAK DIKETAHUI, tetapi 1 = 2, maka selang kepercayaan
(1 – a)100% untuk μ1 – μ2 diberikan oleh:
Dimana:
Sp= taksiran gabungan dari
simpangan baku populasi
2
)
1
(
)
1
(
2
1
2
2
2
2
1
1
2
n
n
s
n
s
n
Sp
Dengan ν = n1 + n2-2.
2
1
2
/
2
1
2
1
2
1
2
/
2
1
1
1
)
(
1
1
)
(
n
n
Sp
t
x
x
n
n
Sp
t
x
x
a
a
25. Ketiga:
Interval taksiran selisih rataan
jika simpangan baku 1 dan 2TIDAK DIKETAHUI
tetapi 1≠2
Jika 𝑥1 dan 𝑠1
2
, dan 𝑥2 dan 𝑠2
2
, masing-masing rataan dan variansi sampel kecil
bebas berukuran n1 dan n2 dari distribusi hampiran normal dengan variansi
tidak diketahui dan tidak sama, maka selang kepercayaan hapiran (1-a)100%
untuk μ1 – μ2 diberikan oleh:
Dengan:
)]
1
/(
)
/
[(
)]
1
/(
)
/
[(
)
/
/
(
2
2
2
2
2
1
2
1
2
1
2
2
2
2
1
2
1
n
n
s
n
n
s
n
s
n
s
2
2
2
1
2
1
2
/
2
1
2
1
2
2
2
1
2
1
2
/
2
1 )
(
)
(
n
s
n
s
t
x
x
n
s
n
s
t
x
x
a
a
26. Latihan 3
Tedapat 2 buah populasi masing-masing terdiri dari bola lampu merek A dan B yang saling bebas, memiliki
standar deviasi σA = 120 jam dan σB = 80 jam. Random sampling terhadap populasi pertama sebanyak nA =
150 buah bola lampu merek A diperoleh rataan 𝑥𝐴 = 1400 jam dan populasi kedua sebanyak nB = 200 buah
bola lampu merek B diperoleh rataan 𝑥𝐵 = 1200 jam.
Pertanyaan:
Carilah taksiran interval kepercayaan 95% dari selisih rataannya kedua populasinya?
Solusi:
Karena 𝑥𝐴 = 1400 dan 𝑥𝐵 = 1200 masing-masing adalah rataan sampel acak berukuran nA = 150 dan nB
=200 yang diambil dari populasi bebas yang simpangan bakunya populasi keduanya diketahui A = 120 jam
dan B = 80 jam, maka interval kepercayaan 95% untuk selisih rataan μ1 – μ2 merupakan contoh dari kasus
pertama dan oleh karena itu:
Batas-batas interval kepercayaan 95% menggunakan nilai zα/2 = z0.025=1.96 untuk selisih rataan populasinya
(µ1–µ2) adalah :
24.8
200
200
80
150
120
1.96
)
1200
(1400
)
(
2
2
2
2
2
/
B
B
A
A
B
A
n
n
Z
x
x
a
Kesimpulan: Dengan kepercayaan 95% diperoleh taksiran selisih rataan populasi bola lampu merek A dan B
dengan interval antara 175.2 dan 224.8 jam.