Lesson 3 Sampling & Sample Size PDF

Lesson 3 Sampling & Sample Size Dr. Ruben A. Sanchez Associate Professor 2 Recall: In quantitative research Recommended Sample Size? SAMPLE SIZE DETERMINATION Sample Infinite Population = 384.16 = 385 Practice: Assuming you chose a 90% confidence level, 0.6 standard de...

Lesson 3 Sampling & Sample Size Dr. Ruben A. Sanchez Associate Professor 2 Recall: In quantitative research Recommended Sample Size? SAMPLE SIZE DETERMINATION Sample Infinite Population = 384.16 = 385 Practice: Assuming you chose a 90% confidence level, 0.6 standard deviation, and a margin of error (confidence interval) of +/- 4%. Answer? 405.90 Or at least 406 respondents Assumption: This should be remembered clearly that this equation assumes the confidence level of 95% and the proportion of 0.50. Hence, complete ignorance about the behavior of the population.  sample respondents  Answer? Sample size is 1,957 Practice Exercises: 1. What should be the representative sample size if the population from which the sample will be taken is 10,000 and the desired margin of error is 2%. Answer: 2,000 sample respondents. 2. A researcher wants to know the average income of the families living in Barangay A which has 2,500 residents. Calculate the sample size the researcher will need if a 5% margin of error is allotted. Answer: 344.8 = 345 sample respondents.  What formula to use? Review of related literatures and studies Sampling? Is a process of selection. Advantages of Sampling 1. Can save money 2. Easy to work with smaller 3. Can save time 4. Greater Accuracy Target Population - entire group a researcher is interested in. Sampled population - collection of elements from which the sample is taken Sampling frame - list of sampling units Two Types of Sampling A. Probability Sampling or Random Sampling  process in which the different units in the population have equal probabilities of being chosen. random selection - is performed by selecting a group of subjects (a sample) for study from a larger group (a population). Note: By using a random selection, the likelihood of bias is reduced B. Non-Probability Sampling or non-random sampling  does not involve random selection of samples. Types of Probability Sampling or Random Sampling 1. Simple Random Sampling  it is the basic sampling technique where a group of subjects (a sample) is selected for study from a larger group (a population). Note: The most common techniques are by using strips of paper, the use of a printed table of random numbers, or the use of random numbers generated by many computer programs or scientific calculators 2. Stratified Random Sampling  this sampling method involves dividing the population into homogeneous subgroups and then taking a simple random sample in each subgroup 3. Systematic Random Sampling  method of selecting a sample by taking every kth unit from the population, the first unit is selected at random. Here k is called the sampling interval and the reciprocal 1/k is the sampling fraction. 4. Cluster Random Sampling  this sampling method involves dividing the population into a cluster, usually along geographic boundaries, then randomly taking samples of clusters, and measuring all units within sampled clusters. Types of Non-Probability Sampling or Non-Random Sampling 1. Accidental, Haphazard, or Convenience Sampling  this is one of the most common methods of sampling which is primarily based on the convenience of the researcher. Most examples are interviews conducted frequently by television news programs to get a quick (although non-representative) reading of the public opinion. 2. Purposive Sampling  samples are taken with a purpose in mind. Usually, one or more specific predefined groups are sought All of the methods below can be considered subcategories of purposive sampling methods Modal Instance Sampling Quota Sampling Expert Sampling Heterogeneity Sampling Snowball Sampling What sampling technique to use? Review of related literatures and studies Clarifications/questions? Formative Assessment 2 Blue Book