Share
Explore BrainMass

Mean

5 patients have a mean diastolic blood level of 95 are recruited for a study one month long. After one month the observed mean decline in diastolic blood pressure in these five patients is 4.8 with a standard deviation on 9.
7.32 how many patients would be needed to have a 90% chance of detecting a significant diff using a one tailed test with a significance level of 5%

7.33 Suppose we conduct a study of the preceding hypotheses based on 20 subjects. What is the probability that we will be able to reject H(0) using a one sided test at the 5% level?

Active Placebo active-pla
mean +- sd
average redness score:-0.61+-0.7 -0.04+-0.68 -.57+.86
(visit 2-Visit1 score)

7.83 Suppose we wish to estimate the number of subjects needed in a main study so that there will be a 90% chance of finding a significance level of 0.05 and we expect the active eyes to have a mean redness score 0.5 less than the placebo. How many subjects are needed in the study?

Solution Preview

See the attached file.
7.32 how many patients would be needed to have a 90% chance of detecting a significant diff using a one tailed test with a significance level of 5%

The sample size formula uses three key factors:
(1) the significance level, the level of acceptable risk the researcher is willing to accept that the true margin of error exceeds the acceptable margin of error; i.e., the probability that differences revealed by statistical analyses really do not exist; also known as Type I error.
The alpha level used in determining sample size in this survey is a=1-0.95 =0.05. In the formula, the alpha level is incorporated into the formula by utilizing the t-value for the alpha level selected (e.g., t-value for alpha level of .05 is 1.66 for sample sizes above 120).

(2) ...

Solution Summary

The solution determines how many patients would be needed to have a 90% chance of detecting a significant difference using a one tailed test with a significance level of 5%.

$2.19