25.11.2014 Views

Biostatistics

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

13.6 THE MANN–WHITNEY TEST 695<br />

Dialog<br />

box:<br />

Session command:<br />

Stat Nonparametrics Mann–Whitney MTB > Mann-Whitney 95.0<br />

C1 C2;<br />

SUBC > Alternative 1.<br />

Type C1 in First Sample and C2 in Second Sample.<br />

At Alternative choose less than.<br />

Click OK.<br />

Output:<br />

Mann–Whitney Test and CI: C1, C2<br />

C1 N 15 Median 15.300<br />

C2 N 10 Median 16.550<br />

Point estimate for ETA1 ETA2 is 1.300<br />

95.1 Percent C.I. for ETA1 ETA2 is ( 2.300, 0.600)<br />

W 145.0<br />

Test of ETA1 ETA2 vs. ETA1 ETA2 is significant at 0.0030<br />

The test is significant at 0.0030 (adjusted for ties)<br />

FIGURE 13.6.2 MINITAB procedure and output for Example 13.6.1.<br />

Ranks<br />

y N Mean Rank Sum of Rank<br />

x 1.000000 15 9.67 146.00<br />

2.000000 10 18.00 180.00<br />

Total 25<br />

Test Statistic b<br />

x<br />

Mann-Whitney U<br />

25.000<br />

Wilcoxon W<br />

145.000<br />

Z 2.775<br />

Asymp. Sig. (2-tailed)<br />

.006<br />

Exact Sig. [2*(1-tailed Sig.)]<br />

.004 a<br />

a. Not corrected for ties<br />

b. Grouping Variable: y<br />

FIGURE 13.6.3 SPSS output for Example 13.6.1.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!