Sample Size & Power Calculation Help for

Dissertation Students & Researchers


What is Sample Size?

     Sample size refers to the number of subjects or participants studied in a trial, including the treatment and control groups, where applicable. Sample size refers to the specific size of the group or groups being studied in your research. The intended sample size is the number of participants planned to be included in your study. This number is not arbitrary and sample size is usually determined by using a power analysis.


     The sample size should be adequate to provide a high probability of detecting as significant an effect size of a given magnitude if such an effect actually exists. Once you have conducted a power analysis you will know the exact sample size needed for your study. The achieved sample size is the number of participants that are actually enrolled in or complete the study. Generally, the larger the sample size, the more reliable the study results are, and the more likely it is that the results can be generalized to other people.  Calculate Your Sample Size Today
Why Calculating Sample Size is Important

     A power analysis can help you determine how large of a sample you need to make accurate statistical conclusions. To determine if a statistical test will have adequate power, analyses to calculate how large of a sample is required must be conducted before you begin your study. Sample size calculation can provide you with the appropriate number of participants you will need to address your research question properly.  Determining sample size is a very important issue because samples that are too large may waste time, resources and money, while samples that are too small may lead to inaccurate results. Without a power analysis, you will not know if your proposed sample size is too large or too small.


     A sample size that is too small will not allow you to properly address your research questions with your proposed statistical analysis. A sample size that is too large will cause you to waste important time or financial resources. To avoid either of these scenarios, you must conduct a power analysis. Calculating sample size can help you determine the ability of your study to detect any effects. We can conduct your power analysis for you to determine the sample size needed to adequately address your research question using the appropriate statistical test(s). This information is important for any study and can save you valuable resources and time.  Determine Your Sample Size Today
How to Determine Sample Size

     Sample size is generally calculated with a power analysis. To calculate your sample size you will need certain information. The information needed to calculate sample size will depend on the statistical test you plan to use. Irrespective of the statistical test you plan to use in your study, you will need to know the desirable effect size to determine sample size. Remember that it takes huge samples to detect tiny differences but tiny samples to detect huge differences, so you have to specify the size of the effect you are trying to detect.  You will also need to know the alpha level you want to use for the statistical test (e.g. alpha=.05) to determine sample size. If you plan to use regression analysis in your study you will need to know the number of predictors that will be included in your regression model to calculate sample size.  Calculate Your Sample Size Today
Let Us Help You Calculate Sample Size

      We recommend consulting with someone who is knowledgeable about sample size calculation and who can explain the various components of conducting a power analysis. Sample size calculation will also vary depending on the type of statistical test you are using. Given the importance of determining sample size, it is important that sample size calculations are conducted properly. If you are unsure about the steps mentioned, then let us help you calculate your study's sample size. We can also help you decide which statistical tests to choose for your study. 

Calculate Your Sample Size Today