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ERIC Number: ED088952
Record Type: Non-Journal
Publication Date: 1974-Apr
Pages: 19
Abstractor: N/A
Reference Count: N/A
[Procedures for Testing Differences Between Means in the Presence of Unequal N's and Variances].
Kohr, Richard L.; Games, Paul A.
An empirical sampling study investigated six procedures for testing differences between means in the presence of unequal n's and variances. Support was obtained for previous research which found t robust to heterogeneous variances only when n's are equal and of moderate size. The procedure which emerged as providing the best control over Type I errors while maintaining satisfactory power in all test conditions was the Behrens-Fisher v statistic with Welch's solution for degrees of freedom (df). The general recommendations when the population variances are unknown are: (1) when n's are the same and equal to or greater than 20 it is permissible to use the t statistic with df = 2n - 2, but when n is less than 20 use v with Welch's solution for df; (2) when n's are unequal use the v statistic with the Welch adjustment for df. (Author)
Publication Type: N/A
Education Level: N/A
Audience: N/A
Language: N/A
Sponsor: N/A
Authoring Institution: N/A