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British Standards Institution Study Day Sample size for clinical trials
手脚印Martin Bland
Prof.of Health Statistics
University of York
Outcome variables for trials
An outcome variable is one which we hope to change, predict or estimate in a trial.
Examples:
Systolic blood pressure in a hypertension trial
Cæsarean ction rate in an obstetric trial
Survival time in a cancer trial
Number of outcome variables
飞人乔丹Should I have few or many?
Many outcome variables2克拉钻戒多少钱
•Cover all possibilities
•Less likely to miss something
•Risk of fal positives
Few outcome variables
•Easier and quick to check and analy
•Cheaper
•Easier for rearch subjects
•Avoid multiple testing
牛尾煲
usually.
Relationship between:
•power of the test,P
•postulated difference in the population,
•standard error of the sample difference,SE(d)
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•significance level,α
If we know three of the we can calculate the fourth. SE(d)depends on the particular sample size problem.
材料科学与工程Relationship between:
•power of the test,P
•postulated difference in the population,
•standard error of the sample difference,SE(d)
•significance level,α
If we know three of the we can calculate the fourth.
菠菜猪肝汤的禁忌need258patients in each group.
