In social studies, comparative studies are common and attract many researchers to follow this approach. Methodology and sampling might encounter a researcher when he has just started to plan for such a study.
So how can we design a proper sampling structure for a comparative study?
Designing the sample size in comparative studies involves determining the number of participants or units to include in the study. The sample size is an important consideration because it can affect the power of the study to detect significant differences or associations, the precision of the estimates, and the generalizability of the findings.
There are several factors to consider when designing the sample size in comparative studies, including the research question, study design, statistical analysis, effect size, variability, and alpha and beta levels. Some common methods for determining sample size include power analysis, sample size calculation, and rule of thumb.
Power analysis involves estimating the sample size required to achieve a certain level of statistical power, which is the probability of detecting a true effect if one exists. The power calculation takes into account the expected effect size, level of significance (alpha), and the desired power level (usually 80% or 90%).
Sample size calculation involves estimating the sample size needed to achieve a certain level of precision in the estimates, usually based on the desired margin of error or confidence interval width.
The rule of thumb suggests that larger sample sizes are generally better than smaller sample sizes, but there are no hard and fast rules about how large a sample size should be. As a general guideline, a sample size of at least 30 per group is often recommended to ensure reliable statistical inference, but the appropriate sample size will depend on the specifics of the study design and research question.
Ultimately, the sample size should be chosen based on careful consideration of the research question, study design, and statistical analysis, as well as practical considerations such as feasibility and resource availability. It is often useful to consult with a statistician or other expert to determine an appropriate sample size for a given study.
Get a copy of Schaefer Mendenhall et al Elementary Survey Sampling and read it. David Booth
What kind of comparative research do you have in mind? Survey based approaches are quite different from qualitative case studies
There are many identified formulas for calculating sample size for comparative studies. My concern is what are the names for these formulas for empirical evidences and reference purposes
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