Tentative Quantitative Research Question
Download G*Power and play around with it. See how changes in assumptions and
parameters affect sample size estimates.
Submit:
 Calculate the sample size needed given these factors:
 onetailed ttest with two independent groups of equal size
 small effect size (see Piasta, S.B., & Justice, L.M., 2010)
 alpha =.05
 beta = .2
 Assume that the result is a sample size beyond what you can obtain. Use the
compromise function to compute alpha and beta for a sample half the size.
Indicate the resulting alpha and beta. Present an argument that your study is
worth doing with the smaller sample.
 Calculate the sample size needed given these factors:

 Calculate the sample size needed given these factors:
 ANOVA (fixed effects, omnibus, oneway)
 small effect size
 alpha =.05
 beta = .2
 3 groups
 Assume that the result is a sample size beyond what you can obtain. Use the
compromise function to compute alpha and beta for a sample approximately half
the size. Give your rationale for your selected beta/alpha ratio. Indicate the
resulting alpha and beta. Give an argument that your study is worth doing with
the smaller sample.
 In a few sentences, describe two designs that can address your research
question. The designs must involve two different statistical analyses. For each
design, specify and justify each of the four factors and calculate the estimated
sample size you’ll need. Give reasons for any parameters you need to specify for
G*Power.
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