Sampling Techniques Module 5Santa Rosa Science And Technology High School Basic Statistics Ms. Ma. Cristina C. Pegollo
Sample ProblemSuppose Ms. Bambasi wants to determine the weekly food expenditure of students, if there are 1000 students and the guidance counselor decided to use only 100 students as a sample, who will be included in the sample?
DEFINITIONSampling technique is aprocedure used to determinethe individuals or members of asample.
PROBABILITY Sampling each eligible member of the population has a specific and known chance of being included in the sample.When using this technique, it is important to have a complete list of the members of the population
NON-PROBABILITY SamplingMembers of the sample size are drawn based on the judgment of the researcher.Sometimes, referred to as subjective sampling.
Probability Sampling1. Simple Random Sampling Lottery Method - write the names or codes on a piece of paper, put them in a container, then randomly select the desired number of samples. Sometimes referred to as the fishbowl technique.
Probability Sampling1. Simple Random Sampling Random Numbers – a table of random numbers, computer or calculator can be used to generate random numbers. This is perhaps a more convenient way of selecting your random sample. The randomly produced digits can be used to pick your samples. However, a complete listing of the members of the population is needed.
Probability Sampling2. Systematic Sampling – choose a starting point then select every kth element of the population using
ExampleChoose a sample of size 5 from N = 45, using systematic random sampling.Solution:Step 1: Determine k; , this means that you have to include every 9th member of the population after choosing a random start.Step 2: You can employ the lottery method to get a random start. Suppose you picked 4.Step 3: Getting 5 members you will have: 4, 13, 22, 31, and 40
Probability Sampling3. Stratified Random Sampling – the population is subdivided into at least two different subpopulations (or strata) that share the same characteristics (such as gender), then draw a sample from each stratum.
ExampleBrgy. Market Area consists of 10,000 families belonging to different income brackets. A survey to find out how many are in favor of the RH bill will be conducted. To ensure that all income groups are represented, respondents will be divided into High-Income, Average-Income, and Low-Income. Below is the distribution of income groups. Strata Number of Families High – Income 2 000 Average – Income 5 000 Low-Income 3 000 N = 10 000
Cont… 1. Using a 5% margin of error, how many families should be included in the sample? Using Slovin’s Formula, you should get 385. 2. Using either proportional or equal allocation , how many from each group should be taken as samples? See the table below Strata Number Percent Proportional Equal of FamiliesHigh-Income 2 000 0.2(385) = 77 385/3 = 128 Average- 5 000 0.5(385) = 129 Income 193Low- Income 3 000 0.3(385) = 128 115 10 000 100% 385 385
Probability Sampling4.Cluster Sampling – divide the population area into sections (or clusters), then randomly select a few of those sections, and then you randomly select a sample from those selected sections.
ExampleSuppose we want to determine the average daily expenses of families living in the City of Santa Rosa. Assume that there are 15 barangays. We can draw a random sample of 5 barangays using random sampling and then get a certain number of families from each of the 5 barangays.
Probability Sampling5. Multi-Stage Sampling – combination of several sampling techniques discussed.
Non-Probability Sampling1. Convenience Sampling – simply use results that are readily available. Hey! Do you believe in love at first sight?
Non-Probability Sampling2. Quota Sampling - the researcher first identifies the stratums and their proportions as they are represented in the population. Then convenience or judgment sampling is used to select the required number of subjects from each stratum. Selected through researcher’s convenience or judgment.
Non-Probability Sampling3. Purposive Sampling – selects members or elements based on the particular purpose of the experiment or study. This technique is useful for situations where you need to reach a targeted sample quickly and where sampling for proportionality is not the primary concern.
Sample Problem Suppose Ms. Bambasi wants to determine the weekly food expenditure of students, if there are 1000 students and the guidance counselor decided to use only 100 students as a sample, who will be included in the sample?Activity. With your partner, help Ms.Bambasi decide on which samplingtechnique she should use in selectingstudents for her sample. Present herthree choices. (Bond Paper)
Exercises:Identify which sampling technique was used in the following scenarios.1. When she wrote Women and Emoticons, author KC Pascual based conclusions on 4500 responses from 100,000 questionnaires distributed to women.2. The Guidance Counselor at Santa Rosa High School surveys all students from each of 20 randomly selected classes.3. A sociologist at the College of StaRSci selects 15 men and 15 women from each of 4 Math Classes.
Cont…4. IBM selects every 200th compact disk from the assembly line ad conducts a thorough test of quality.5. The court secretary writes the name of each Municipal Judge on a separate card, shuffles the cards , and then draws 3 names.6. The marketing manager of Ebay.ph tests a new sales strategy by randomly selecting 150 consumers with less than P100 000 in gross income and 150 consumers with gross income of at least P100 000.7. Pro-RH bill lobbyists polls 300 men and 300 women about their views concerning the use of contraceptives.
Cont.8. A market researcher for Champion Detergent interviews all passengers on each of 10 randomly selected PUVs.9. A medical researcher from Multiliver Phils. interviews all leukemia patients in each of 20 randomly selected hospitals.10. In conducting research for the evening news, a reported for ABC-CBN interviews 15 people as they leave SM Santa Rosa.
B. Solve the following1. A researcher would like to investigate the perception of students of Mathematics. He divided the population into sub-populations as shown below. Use stratified random sampling if the sample to be drawn consists of 500 students. Strata Number of Students First Year 1600 Second Year 1500 Third Year 1400 Fourth Year 1000
2. A journalist would like to know the most favorite noontime show for this month. He decided to conduct a survey on 5 barangays. The table below shows the list of barangay and the number of residents in each barangay. Use stratified random sampling to draw 1 000 residents who will be included in the survey. Barangay Number of Residents Mapayapa 2 000 Malinis 1 000 Mahangin 1 500 Mabunga 2 500 Masaya 1 500