This document discusses measures of variability used in statistics. It defines variability as the spread or dispersion of scores. The key measures of variability discussed are the range, variance, and standard deviation. The range is the difference between the highest and lowest scores. The variance is the average of the squared deviations from the mean and represents how far the scores deviate from the mean. The standard deviation is the square root of the variance and represents how much scores typically deviate from the mean. Larger standard deviations indicate greater variability in the scores.
Topic: Variance
Student Name: Sonia Khan
Class: B.Ed. 2.5
Project Name: “Young Teachers' Professional Development (TPD)"
"Project Founder: Prof. Dr. Amjad Ali Arain
Faculty of Education, University of Sindh, Pakistan
Topic: Variance
Student Name: Sonia Khan
Class: B.Ed. 2.5
Project Name: “Young Teachers' Professional Development (TPD)"
"Project Founder: Prof. Dr. Amjad Ali Arain
Faculty of Education, University of Sindh, Pakistan
Normal Distribution – Introduction and PropertiesSundar B N
In this video you can see Normal Distribution – Introduction and Properties.
Watch the video on above ppt
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Subscribe to Vision Academy
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students will be able to understand various measures of central tendency and also will be able to calculate mean median and mode for individual discrete and continuous series.
Unit-I Measures of Dispersion- Biostatistics - Ravinandan A P.pdfRavinandan A P
Biostatistics, Unit-I, Measures of Dispersion, Dispersion
Range
variation of mean
standard deviation
Variance
coefficient of variation
standard error of the mean
Normal Distribution – Introduction and PropertiesSundar B N
In this video you can see Normal Distribution – Introduction and Properties.
Watch the video on above ppt
https://www.youtube.com/watch?v=ocTXHLWsec8&list=PLBWPV_4DjPFO6RjpbyYXSaZHiakMaeM9D&index=4
Subscribe to Vision Academy
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students will be able to understand various measures of central tendency and also will be able to calculate mean median and mode for individual discrete and continuous series.
Unit-I Measures of Dispersion- Biostatistics - Ravinandan A P.pdfRavinandan A P
Biostatistics, Unit-I, Measures of Dispersion, Dispersion
Range
variation of mean
standard deviation
Variance
coefficient of variation
standard error of the mean
Unit 8 - Information and Communication Technology (Paper I).pdfThiyagu K
This slides describes the basic concepts of ICT, basics of Email, Emerging Technology and Digital Initiatives in Education. This presentations aligns with the UGC Paper I syllabus.
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
The Roman Empire A Historical Colossus.pdfkaushalkr1407
The Roman Empire, a vast and enduring power, stands as one of history's most remarkable civilizations, leaving an indelible imprint on the world. It emerged from the Roman Republic, transitioning into an imperial powerhouse under the leadership of Augustus Caesar in 27 BCE. This transformation marked the beginning of an era defined by unprecedented territorial expansion, architectural marvels, and profound cultural influence.
The empire's roots lie in the city of Rome, founded, according to legend, by Romulus in 753 BCE. Over centuries, Rome evolved from a small settlement to a formidable republic, characterized by a complex political system with elected officials and checks on power. However, internal strife, class conflicts, and military ambitions paved the way for the end of the Republic. Julius Caesar’s dictatorship and subsequent assassination in 44 BCE created a power vacuum, leading to a civil war. Octavian, later Augustus, emerged victorious, heralding the Roman Empire’s birth.
Under Augustus, the empire experienced the Pax Romana, a 200-year period of relative peace and stability. Augustus reformed the military, established efficient administrative systems, and initiated grand construction projects. The empire's borders expanded, encompassing territories from Britain to Egypt and from Spain to the Euphrates. Roman legions, renowned for their discipline and engineering prowess, secured and maintained these vast territories, building roads, fortifications, and cities that facilitated control and integration.
The Roman Empire’s society was hierarchical, with a rigid class system. At the top were the patricians, wealthy elites who held significant political power. Below them were the plebeians, free citizens with limited political influence, and the vast numbers of slaves who formed the backbone of the economy. The family unit was central, governed by the paterfamilias, the male head who held absolute authority.
Culturally, the Romans were eclectic, absorbing and adapting elements from the civilizations they encountered, particularly the Greeks. Roman art, literature, and philosophy reflected this synthesis, creating a rich cultural tapestry. Latin, the Roman language, became the lingua franca of the Western world, influencing numerous modern languages.
Roman architecture and engineering achievements were monumental. They perfected the arch, vault, and dome, constructing enduring structures like the Colosseum, Pantheon, and aqueducts. These engineering marvels not only showcased Roman ingenuity but also served practical purposes, from public entertainment to water supply.
Welcome to TechSoup New Member Orientation and Q&A (May 2024).pdfTechSoup
In this webinar you will learn how your organization can access TechSoup's wide variety of product discount and donation programs. From hardware to software, we'll give you a tour of the tools available to help your nonprofit with productivity, collaboration, financial management, donor tracking, security, and more.
Embracing GenAI - A Strategic ImperativePeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
Introduction to AI for Nonprofits with Tapp NetworkTechSoup
Dive into the world of AI! Experts Jon Hill and Tareq Monaur will guide you through AI's role in enhancing nonprofit websites and basic marketing strategies, making it easy to understand and apply.
Palestine last event orientationfvgnh .pptxRaedMohamed3
An EFL lesson about the current events in Palestine. It is intended to be for intermediate students who wish to increase their listening skills through a short lesson in power point.
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
Macroeconomics- Movie Location
This will be used as part of your Personal Professional Portfolio once graded.
Objective:
Prepare a presentation or a paper using research, basic comparative analysis, data organization and application of economic information. You will make an informed assessment of an economic climate outside of the United States to accomplish an entertainment industry objective.
2. Variability
Limits of Central Tendencies: Mode, Mean, Median
They offer a limited view of data set.
Example: Weather in Honolulu and Phoenix
Same Mean Temperature: 75°
Variability?
But how are yearly temperatures distributed on the mean? What is the
range of yearly temperatures?
4. Measures of Variability
Measures of variability tell us:
• The extent to which the scores differ from each other or how
spread out the scores are.
• How accurately the measure of central tendency describes the
distribution.
• The shape of the distribution.
5. Measures of Variability
Some Definitions:
Population (universe) is the collection of things under consideration
Sample is a portion of the population selected for analysis
Statistic is a summary measure computed to describe a
characteristic of the sample
6. Measures of Variability
Just what is variability?
Variability is the spread or dispersion of scores.
Measuring Variability
There are a few ways to measure variability and they include:
1) The Range
2) The Mean Deviation
3) The Standard Deviation
4) The Variance
7. Variability
Measures of Variability
Range: The range is a measure of the distance between
highest and lowest.
R= H – L
Temperature Example:
Range:
Honolulu: 89° – 65° 24°
Phoenix: 106° – 41° 65°
8. The Range
The simplest and most straightforward measurement of variation is the
range which measures variation in interval-ratio variables.
Range = highest score – lowest score
R = H – L
9. Range: Examples
If the oldest person included in a study was 89 and the youngest was
18, then the range would be 71 years.
Or, if the most frequent incidences of disturbing the peace among 6
communities under study is 18 and the least frequent incidences
was 4, then the range is 14.
10. Okay, so now you tell me the range…
This table indicates the number of
metropolitan areas, as defined
by the Census Bureau, in six
states.
What is the range in the number
metropolitan areas in these six
states?
– R=H-L
– R=9-3
– R=6
Delaware 3
Idaho 4
Nebraska 4
Kansas 5
Iowa 4
Montana 3
California 9
11. Variance and Standard Deviation
Variance: is a measure of the dispersion of a sample (or how
closely the observations cluster around the mean [average]). Also
known as the mean of the squared deviations.
Standard Deviation: the square root of the variance, is the measure
of variation in the observed values (or variation in the clustering
around the mean).
12. The Variance
Remember that the deviation is the distance of any given score from
its mean.
The variance takes into account every score.
But if we were to simply add them up, the plus and minus (positive and
negative) scores would cancel each other out because the sum of
actual deviations is always zero!
)
( X
X
0
)
(
X
X
13. So, what we should we do?
We square the actual deviations and then add them together.
– Remember: When you square a negative number it becomes
positive!
SO,
S2 = sum of squared deviations divided by the number of scores.
The variance provides information about the relative variability.
The Variance
14. Variance: Weeks on Unemployment:
X
(weeks)
Deviation:
(raw score from the
mean, squared)
9
8
6
4
2
1
9-5= 4
8-5=3
6-5=1
4-5=-1
2-5=-3
1-5=-4
42 = 16
32 = 9
12 = 1
-12 = 1
-32 = 9
-42 = 16
ΣX=30
χ= 30=5
6
Step 1: Calculate
the Mean
Step 3: Calculate
Sum of square Dev
Step 2: Calculate
Deviation
15. The mean of the squared deviations is the same as the variance,
and can be symbolized by s2
scores
of
number
total
mean
the
from
deviations
squared
the
of
sum
variance
where
N
X
X
s
2
2
)
(
The Variance
16. Variance: Weeks on Unemployment:
X
(weeks)
Deviation:
(raw score from the
mean, squared)
Variance:
9
8
6
4
2
1
9-5= 4
8-5=3
6-5=1
4-5=-1
2-5=-3
1-5=-4
42 = 16
32 = 9
12 = 1
-12 = 1
-32 = 9
-42 = 16
(weeks squared)
ΣX=30
χ= 30=5
6
Step 1: Calculate
the Mean
Step 3: Calculate
Sum of square Dev
Step 2: Calculate
Deviation
Step 4: Calculate
the Mean of squared dev.
17. Standard Deviation:
It is the typical (standard) difference (deviation) of an observation
from the mean.
Think of it as the average distance a data point is from the mean,
although this is not strictly true.
What is a standard deviation?
18. Standard Deviation:
The standard deviation is calculated by taking the square root of the
variance.
What is a standard deviation?
19. Variance: Weeks on Unemployment:
X
(weeks)
Deviation:
(raw score from the
mean, squared)
Variance: Standard Deviation:
(square root of the variance)
9
8
6
4
2
1
9-5= 4
8-5=3
6-5=1
4-5=-1
2-5=-3
1-5=-4
42 = 16
32 = 9
12 = 1
-12 = 1
-32 = 9
-42 = 16
(weeks squared)
ΣX=30
χ= 30=5
6
s = 2.94
Step 1: Calculate
the Mean
Step 3: Calculate
Sum of square Dev
Step 2: Calculate
Deviation
Step 4: Calculate
the Mean of squared dev.
Step 5: Calculate the
Square root of the Var.
20. Variance: Weeks on Unemployment:
X
(weeks)
Deviation:
(raw score from the
mean, squared)
Variance: Standard Deviation:
s =√Σ(X - χ )2
N
(square root of the variance)
9
8
6
4
2
1
9-5= 4
8-5=3
6-5=1
4-5=-1
2-5=-3
1-5=-4
42 = 16
32 = 9
12 = 1
-12 = 1
-32 = 9
-42 = 16
(weeks squared)
____
√ 8.67
ΣX=30
χ= 30=5
6
s = 2.94
Step 1: Calculate
the Mean
Step 3: Calculate
Sum of square Dev
Step 2: Calculate
Deviation
Step 4: Calculate
the Mean of squared dev.
Step 5: Calculate the
Square root of the Var.
21. Two Ways to Look at Standard Deviation: Sample and
Population
22. S2 = sum of squared deviations divided by the number of scores.
The Variance
23. Some Things to Remember about Sample Variance
Uses the deviation from the mean
Remember, the sum of the deviations always equals zero, so you
have to square each of the deviations
S2= sum of squared deviations divided by the number of scores
Provides information about the relative variability
24. It is the typical (standard) difference (deviation) of an observation
from the mean.
Think of it as the average distance a data point is from the mean,
although this is not strictly true.
What is a standard deviation?
25. Two Ways to Look at Standard Deviation: Sample and
Population
26. Variability
Weeks on Unemployment: Standard Deviation (S)
Thus, in this example, “the distribution deviates from the mean by nearly 3
weeks.” In other words, on average…the scores in this distribution
deviate from the mean by nearly 3 weeks.” (71)
Judges and Sentencing:
You are an attorney with a choice of judges:
Judge A: gives all defendants convicted of assault 24 months
Judge B: gives all defendants convicted of assault 6-months to 6 years
depending on priors.
27. Prison Sentences: Judge A
X
(months)
X - χ Deviation:
(X – χ)2
(raw score from the mean,
squared)
Variance:
S2 =Σ(X – χ)2
N
(“the mean of the squared
deviation.”)
Stand. Deviation:
S =√Σ(X - χ )2
N
(square root of the variance)
34
30
31
33
36
34
34-33= 1
30-33=-3
31-33=-2
33-33=0
36-33=3
34-33=1
12 = 1
-32 = 9
-22 = 4
02 = 0
32 = 9
12 = 1
24= 4.0
6
(months squared)
____
√ 4.0
ΣX=198
χ= 198= 33
6
Σ(X – χ)2 = 24 S = 2.0
Step 1: Calculate
the Mean
Step 2: Calculate
Deviation
Step 3: Calculate
Sum of square Dev
Step 4: Calculate
the Mean of squared dev.
Step 5: Calculate the
Square root of the Var.
28. Prison Sentences: Judge B
X
(months)
X - χ Deviation:
(X – χ)2
(raw score from the mean,
squared)
Variance:
S2 =Σ(X – χ)2
N
(“the mean of the squared
deviation.”)
Stand. Deviation:
S =√Σ(X - χ )2
N
(square root of the variance)
26
43
22
35
20
34
36-30= -6
43-30=13
22-30=-8
35-30=5
20-30=-10
34-30=4
-62 = 36
132 = 169
-82 = 64
52 = 25
102 = 100
42 = 8
402= 67.0
6
(months squared)
____
√ 67.0
ΣX=180
χ=180= 30
6
Σ(X – χ)2
=402
S = 8.18
Step 1: Calculate
the Mean
Step 2: Calculate
Deviation
Step 3: Calculate
Sum of square Dev
Step 4: Calculate
the Mean of squared dev.
Step 5: Calculate the
Square root of the Var.
29. Variability
Judges and Sentences:
Judge A has a larger mean, smaller variance and standard
deviation. “Judge A seems harsher but fairer. Judge B is more
lenient but more inconsistent.” (74)
Thus Judge A would be a better judge to face. Their mean is larger
(so you will get a longer sentence) but are less likely to get longer
sentence than if you faced Judge B.
30. Standard Deviation
Is the square root of the variance.
Uses the same units of measurement as the raw scores.
Tells how much scores deviate below and above the mean
31. Standard Deviation
Standard Deviation: Applications
Standard deviation also allows us to:
1) Measure the baseline of a frequency polygon.
2) Find the distance between raw scores and the mean – a
standardized method that permits comparisons between raw scores
in the distribution – as well as between different distributions.
32. Standard Deviation
Standard Deviation: Baseline of a Frequency Polygon.
The baseline of a frequency polygon can be measured in units of
standard deviation.
Example:
= 80
s = 5
Then, the raw score 85 lies
one Standard Deviation
above the mean (+1s).
33. Standard Deviation
Standard Deviation: The Normal Range
Unless highly skewed, approximately two-thirds of scores within a
distribution will fall within the one standard deviation above and
below the mean.
Example: Reading Levels
Words per minute.
= 120
s = 25
34.
35.
36.
37. The deviation (definitional) formula for the population standard
deviation
N
X
X
2
The larger the standard deviation the more variability there is
in the scores
The standard deviation is somewhat less sensitive to extreme
outliers than the range (as N increases)
Standard Deviation
38.
N
X
X
S
2
What’s the difference between this formula and the
population standard deviation?
The deviation (definitional) formula for the sample standard deviation
In the first case, all the Xs represent the entire population. In the
second case, the Xs represent a sample.
Standard Deviation
39. Calculating S using the Raw-Score Formula
N
N
X
X
S
2
2
To calculate ΣX2 you square all the scores first and then sum them
To calculate (ΣX)2 you sum all the scores first and then square them
Standard Deviation
40. The Raw-Score Formula: Example
N
N
X
X
S
2
2
X X2
21
25
24
30
34
X = 134
441
625
576
900
1151
X2 = 3698
5
5
134
3698
2
S
5
2
.
3591
3698
S
62
.
4
36
.
21
S
41. Application to Normal Distribution
Knowing the standard deviation
you can describe your sample
more accurately
Look at the inflection points of the
distribution
42.
43.
44. A Note about Transformations:
Adding or subtracting just shifts the distribution, without changing the
variation (variance).
Multiplying or dividing changes the variability, but it is a multiple of the
transformation
Transformations can be useful when scores are skewed from the
“mean” that the researcher prefers to work with. Also,
transformations can be helpful when comparing multiple sets of
scores.
46. A note on N vs. n and N vs. n+1
N is used to represent the number of scores in a population. Some
authors also use it to represent the number of scores in a sample as
well.
n is used to represent the number of scores in a sample.
When calculating the variance and standard deviation, you will
sometimes see N + 1 or n + 1 instead of N or n.
N+1 or n+1 is used by many social scientists when computing from a
sample with the intention of generalizing to a larger population.
N+1 provides a better estimate and is the formula used by SPSS.
47. Estimating the population
standard deviation from a sample
ŝ
S, the sample standard, is usually a little smaller than the
population standard deviation. Why?
The sample mean minimizes the sum of squared deviations
(SS). Therefore, if the sample mean differs at all from the
population mean, then the SS from the sample will be an
underestimate of the SS from the population
Therefore, statisticians alter the formula of the sample standard
deviation by subtracting 1 from N
48. Variance is Error in Predictions
The larger the variability, the larger the differences between the
mean and the scores, so the larger the error when we use the mean
to predict the scores
Error or error variance: average error between the predicted mean
score and the actual raw scores
Same for the population: estimate of population variance
49. Summarizing Research Using Variability
Remember, the standard deviation is most often the measure of
variability reported.
The more consistent the scores are (i.e., the smaller the variance), the
stronger the relationship.
51. Review: Measures of Variability
Just what is variability?
Variability is the spread or dispersion of scores.
Measuring Variability
There are a few ways to measure variability and they include:
1) The Range
2) The Mean Deviation
3) The Standard Deviation
4) The Variance
52. Review: The Range
Measures of Variability
Range: The range is a measure of the distance between
highest and lowest.
R= H – L
Temperature Example:
Range:
Honolulu: 89° – 65° 24°
Phoenix: 106° – 41° 65°
53. Review: Variance and Standard Deviation
Variance: is a measure of the dispersion of a sample (or how
closely the observations cluster around the mean [average])
Standard Deviation: the square root of the variance, is the measure
of variation in the observed values (or variation in the clustering
around the mean).
54. Review: The Variance
Remember that the deviation is the distance of any given score from
its mean.
The variance takes into account every score.
But if we were to simply add them up, the plus and minus (positive and
negative) scores would cancel each other out because the sum of
actual deviations is always zero!
)
( X
X
0
)
(
X
X
55. So, what we should we do?
We square the actual deviations and then add them together.
– Remember: When you square a negative number it becomes
positive!
SO,
S2 = sum of squared deviations divided by the number of scores.
The variance provides information about the relative variability.
Review: The Variance
56. Review: Variance: Weeks on Unemployment:
X
(weeks)
Deviation:
(raw score from the
mean, squared)
9
8
6
4
2
1
9-5= 4
8-5=3
6-5=1
4-5=-1
2-5=-3
1-5=-4
42 = 16
32 = 9
12 = 1
-12 = 1
-32 = 9
-42 = 16
ΣX=30
χ= 30=5
6
Step 1: Calculate
the Mean
Step 3: Calculate
Sum of square Dev
Step 2: Calculate
Deviation
57. The mean of the squared deviations is the same as the variance,
and can be symbolized by s2
scores
of
number
total
mean
the
from
deviations
squared
the
of
sum
variance
where
N
X
X
s
2
2
)
(
Review: The Variance
58. Review: Variance: Weeks on Unemployment:
X
(weeks)
Deviation:
(raw score from the
mean, squared)
Variance:
9
8
6
4
2
1
9-5= 4
8-5=3
6-5=1
4-5=-1
2-5=-3
1-5=-4
42 = 16
32 = 9
12 = 1
-12 = 1
-32 = 9
-42 = 16
(weeks squared)
ΣX=30
χ= 30=5
6
Step 1: Calculate
the Mean
Step 3: Calculate
Sum of square Dev
Step 2: Calculate
Deviation
Step 4: Calculate
the Mean of squared dev.
59. Standard Deviation:
It is the typical (standard) difference (deviation) of an observation
from the mean.
Think of it as the average distance a data point is from the mean,
although this is not strictly true.
Review: Standard Deviation
61. Review: Standard Deviation: Weeks on Unemployment:
X
(weeks)
Deviation:
(raw score from the
mean, squared)
Variance: Standard Deviation:
(square root of the variance)
9
8
6
4
2
1
9-5= 4
8-5=3
6-5=1
4-5=-1
2-5=-3
1-5=-4
42 = 16
32 = 9
12 = 1
-12 = 1
-32 = 9
-42 = 16
(weeks squared)
ΣX=30
χ= 30=5
6
s = 2.94
Step 1: Calculate
the Mean
Step 3: Calculate
Sum of square Dev
Step 2: Calculate
Deviation
Step 4: Calculate
the Mean of squared dev.
Step 5: Calculate the
Square root of the Var.