Table 2.

Sample size requirements for power levels of 0.8 and 0.9 based on prior studies of Cooking with Kids

Measure	Clinically relevant change	Minimum sample size/groupa
		1 - β = 0.8	1 - β = 0.9
Student attitude	2	50	66
Student self-efficacy	2	108	144
Student FV preference	3	127	170
Parent modeling	2	64	86
Parent self-efficacy	4	110	146
Parent FV availability	2	15	20
Parent eating competence	3	105	140

^aBased on repeated pre/post measures using standard deviations from previous research. For example, a total of 100 participants are needed in this two-treatment parallel-design study. The probability is 80 % that the study will detect a treatment difference in student attitude at a two-sided 0.05 significance level, if the true difference between treatments is 2 units. This is based on the assumption that the standard deviation of the response variable is 3.5

website: http://hedwig.mgh.harvard.edu/sample_size/js/js_parallel_quant.html