## Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

## If You Use a Screen Reader

This content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.

# A Comparison of the Power of Wilcoxon's Rank-Sum Statistic to That of Student's t Statistic under Various Nonnormal Distributions

R. Clifford Blair and James J. Higgins
Journal of Educational Statistics
Vol. 5, No. 4 (Winter, 1980), pp. 309-335
DOI: 10.2307/1164905
Stable URL: http://www.jstor.org/stable/1164905
Page Count: 27
Preview not available

## Abstract

Computer generated Monte Carlo techniques were used to compare the power of Wilcoxon's rank-sum test to the power of the two independent means t test for situations in which samples were drawn from (1) uniform, (2) Laplace, (3) half-normal, (4) exponential, (5) mixed-normal, and (6) mixed-uniform distributions. Sample sizes studied were $(\underline{\text{n}}_{1},\underline{\text{n}}_{2})$ = (3,9), (6,6), (9,27), (18,18), (27,81), and (54,54). It was concluded that (1) generally speaking, the Wilcoxon statistic held very large power advantages over the t statistic, (2) asymptotic relative efficiencies were reasonably good indicators of the relative power of the two statistics, (3) results obtained from smaller samples were often markedly different from the results obtained from larger samples, and (4) because of the narrow ranges of population shapes and sample sizes investigated in some widely cited previous studies of this type, the conclusions reached in those studies must now be deemed questionable.

• [309]
• 310
• 311
• 312
• 313
• 314
• 315
• 316
• 317
• 318
• 319
• 320
• 321
• 322
• 323
• 324
• 325
• 326
• 327
• 328
• 329
• 330
• 331
• 332
• 333
• 334
• 335