FAQ/Power - CBU statistics Wiki
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Table of sample sizes required for tests of non-zero Kendall, Spearman and Pearson correlations

We assume 90% power and a Type I error of 5%

Null hypothesis : correlation = 0;

Alternative: correlation = non-zero value

If you know the sign of the non-zero correlation the test is one-tailed otherwise it is two-tailed.

Computations using methods in Kraemer, HC & Thiemann, S (1987) How Many Subjects? Statistical Power Analysis in Research. Sage:London.

• Power calculator also available for the Pearson correlation.

• Dunlap WP and Myers L (1997) show that for a Pearson correlation, r, 8/\$\$r^text{2}\$\$ gives a total sample size with at least 80% power.

Correlations of 0.1, 0.3 and 0.5 correspond to small, medium and high correlations using rules of thumb.

 1-tail 2-tail correlation Kendall Spearman Pearson Kendall Spearman Pearson 0.1 1041 1013 854 1277 1111 1047 0.2 224 250 212 274 307 259 0.3 106 107 93 129 130 113 0.4 58 62 51 70 75 62 0.5 37 39 32 44 46 38 0.6 25 26 21 29 30 25 0.7 18 19 15 21 21 17 0.8 13 <14 <10 15 15 12 0.9 9 <10 <10 11 11 <10

Reference

Dunlap WP and Myers L (1997) Approximating Power for significance tests with one degree of freedom. Psychological Methods 2(2) 186-191.

None: FAQ/Power (last edited 2014-03-27 12:23:21 by PeterWatson)