Advanced Nursing Inquiry and Evidence Based Practice

6/15/2021 MAIN_MSN5300_FN2 R_2021-GRAD2: Sample Size

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Why sample size is important:

a study should only be undertaken once there is a realistic chance that the study will yield useful information if sample size is too small, may produce inconclusive results and could also be considered unethical by exposing human subjects or lab animals to needless risk if sample size is too large, will waste scarce resources and could expose more participants than necessary to any related risk appropriate determination of the sample size used in a study is a crucial step in the design of a study

Power Analysis is a mathematical calculation that can be used to determine sample size based on estimation of  3 major factors:  1. Power: probability of detecting relationships that exist in the study population - usually estimate standard power = .80 2. Effect size: extent to which a phenomenon is present in a population - can only be calculated after data collection, estimates of ES are used for power analysis as follows:     < 0.1 = trivial effect; 0.1 - 0.3 = small effect; 0.3 - 0.5 = moderate effect, and > 0.5 = large difference effect  - usually estimate ES = 0.5 (moderate effect)  3. Level of significance (alpha): risk of concluding that a difference exists when there is no actual difference - usually estimate alpha = .05 Knowing 3 constants of 4 allows for calculation of Sample size (n)

 

Last modified: Monday, June 14, 2021, 1:32 AM

6/15/2021 MAIN_MSN5300_FN2 R_2021-GRAD2: Sample Size

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