Sample Size Required for ANOVA

Number of groups (k)

Number of Groups / arms in your study.

Your Guesstimate of Mean and SD in each group.

Group / Arm No	Mean	Standard Deviation	Sample Size Ratio * (SS in the Group / SS in Group 1)
1
2
3

Approximate estimate of Mean and SD in each group, based on previos studies/pilot studies etc.

* Ratio of sample size in each group to ratio of sample size in first group. So, this ratio will always be 1 for group one. For other groups, it should be > = 1. If sample sizes are unequal in the groups, please select the group with lowest intended sample size as group one, to have this ratio for other groups >= 1.

Confidence Level %

In percentage. Commonly used values are 95, 99 and 90. Should be between 0.01 to 99.99.

Power ( 1 - β)

In Percentage. Should be between 0.001 to 99.999. Common values are 80 % and 90 %

Sample Size Required =

Sample Size Determination

Sample Size Required for ANOVA

This utility can be used to calculate required sample size when your aim is to test whether more than two sample means are equal or otherwise. (Null hypothesis: All sample means are equal. Alternate hypothesis: At least two of the sample means are significantly different.