On the use of the generalized <i>t</i> and generalized rank‐sum statistics in medical research

Blair, R. Clifford; Morel, Jorge G.

doi:10.1002/sim.4780110410

Cited by 9 publications

(5 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We did "nd little advantage, in terms of power, for the rank sum test in the contaminated normal cases considered. Blair and Morel's [3] results for the rank sum test in normal cases were qualitatively similar to those here for R J . Speci"cally the rank sum test was less powerful than the generalized t when the variance increases.…”

Section: Discussionsupporting

confidence: 85%

Generalized treatment effects for clinical trials

Hyslop¹,

Anderson²

2000

Statist. Med.

View full text Add to dashboard Cite

Practice in the analysis of clinical trials with continuously measured endpoints is to focus on the difference or percentage change in mean or median response. However, treatments may have effects on the distribution of responses other than on the average response. We sought an approach to such generalized treatment effects that: (i) targets a parameter that is easily understood by our clinical colleagues; and (ii) employs confidence intervals as the basis for inference. We consider one such approach based on work in reliability theory, namely setting Pr[Y>X] as the target parameter, and compare this approach to an earlier one due to O'Brien. The two approaches have similar properties when they both seek to reject the null hypothesis of no effect due to different variances but differ when the larger variance corresponds to the larger mean. In that case, our approach views that the larger variance attenuates the effect of the larger mean. Out suggested approach applies easily to positive control (clinical) equivalence trials. Copyright © 2000 John Wiley & Sons, Ltd.

show abstract

Section: Discussionsupporting

confidence: 85%

Generalized treatment effects for clinical trials

Hyslop¹,

Anderson²

2000

Statist. Med.

View full text Add to dashboard Cite

show abstract

“…Figure 4 shows the differences in power between these tests and the Wilcoxon test for m + n = 100 and A = 0.9, and nl and A? ; *II = (0~20,0~20,0~20,0~20,0~20), ~2 = (0~03,0~06,0~13,0~26,0~52) 'Whitehead's method (9) In addition, Figure 4 shows that in moderate-sized samples the OBrien and Smirnov tests have comparable power, with the O'Brien test generally having a slight edge on the Smirnov test. Figure 5 shows that in smaller samples, especially unbalanced ones, the O'Brien test is consistently more powerful than the Smirnov test.…”

Section: Resultsmentioning

confidence: 81%

The Appropriateness of the Wilcoxon Test in Ordinal Data

Hilton

1996

Statist. Med.

View full text Add to dashboard Cite

In two-sample studies with ordinal responses, the Wilcoxon rank-sum test is generally chosen to test equality of the distributions, in spite of it being a specific test of location shift. I compared the power of the exact tests based on the Wilcoxon statistic, O'Brien's generalized Wilcoxon statistic, and the omnibus Smirnov statistic in the presence of location shift and scale alternatives. All three tests can gain power as a function of the scale parameter, depending on its magnitude relative to the shift parameter. As the relative influence of the scale parameter grows, the O'Brien test is the most powerful. I also compared the power of the asymptotic Wilcoxon test with its exact version, and found that it either inflates or deflates power if there are scale changes present. I present results of a simulation study.

show abstract

“…t-testing and rank sum testing statistics were used to evaluate whether statistically significant changes in the average grain dimensions were produced in spot welds made using different tool designs and rotational speed settings. 14 The tool shoulder and pin temperatures during friction stir spot welding were measured by holding the pin stationary and rotating the AZ31 test samples. Unless otherwise stated, all stir zone temperature measurements were made using the three-flat/0?5 mm/threaded tool design.…”

Section: Methodsmentioning

confidence: 99%

Tool design and stir zone grain size in AZ31 friction stir spot welds

Sun

Yin

Gerlich

et al. 2009

Science and Technology of Welding and Joining

View full text Add to dashboard Cite

The influence of tool design and tool rotational speed variations on the torque, energy output, stir zone temperature and average grain size in the stir zones of AZ31 friction stir spot welds was investigated. The average stir zone grain size decreased by y1 mm in AZ31 friction stir spot welds made using a three-flat/threaded tool design and tool rotational speeds of 2250 and 3000 rev min 21 . However, there was no statistically significant influence of tool design on the average grain sizes in friction stir spot welds made using tool rotational speeds of 1500 and 1000 rev min 21 . There was no evidence of grain growth in the stir zones of AZ31 friction stir spot welds. Similar torque, calculated energy output and stir zone temperature values were found in AZ31 friction stir spot welds made using threaded and three-flat threaded tool designs and tool rotational speeds from 1000 to 3000 rev min 21 .

show abstract

On the use of the generalized t and generalized rank‐sum statistics in medical research

Cited by 9 publications

References 7 publications

Generalized treatment effects for clinical trials

Generalized treatment effects for clinical trials

The Appropriateness of the Wilcoxon Test in Ordinal Data

Tool design and stir zone grain size in AZ31 friction stir spot welds

Contact Info

Product

Resources

About