The following table displays demographic and descriptive statistics on subjects

Question

The following table displays demographic and descriptive statistics on subjects involved in a clinical trial for an experimental medication. Characteristic Experimental Medication (n-100) 47.2 (4.3) 46% 13.1 (2.9) $36.560 ($1,054) 24.7 (2.7) Placebo (n=100) Mean (SD) Age, years % Males Mean (SD) Educational Level, years Mean (SD) Annual Income, $000s Mean Body Mass Index 58% 14.2 (3.1) $37.470 ($998) 25.1 (2.4) Use the following formula to calculate the confidence interval for this question what is the 95% CI for the mean age for persons assigned to the placebo group? a. (46.34,48.04) b. (-1.96,1.96) c. (-2.10,2.41) d. (45.10,47.10) The following table displays demographic and descriptive statistics on subjects involved in a clinical trial for an experimental medication. Experimental Medication (n-100) 47.2 (4.3) 46% 13.1 (2.9) $36.560 (S1,054) 24.7 (2.7) Placebo (n-100) Mean (SD) Age, years % Males Mean (SD) Mean (SD) Annual Income, $000s Mean Body Mass Index 58% 14.2 (3.1) 37.470 ($998) 25.1 (2.4) I Level, years Use the following formula to calculate the confidence interval for this question: What is the 95% confidence interval for the difference in mean ages in patients assigned to the experimental versus the placebo groups? (Quiz help: Sp = 4.72) a. (7.0,9.0) b. (-0.21,2.41) (-1.96,1.96) d. (45.10,47.10)

Explanation / Answer

Ans:

critical t value==TINV(0.05,99)=1.984

standard dev=5.1

Confidence interval for mean age of placebo group

=46.1+/-1.984*5.1/sqrt(100)

=46.1+/-1.0098

=(45.10,47.10)

Option d is correct.

sp=sqrt((99*4.3^2+99*5.1^2)/(100+100-2))=4.717

df=100+100-2=198

critical t value=tinv(0.05,198)=1.97

Confidence interval for difference in mean ages:

=(47.2-46.1)+/-1.972*4.717*sqrt(2/100)

=1.1+/-1.31

=(-0.21,2.41)

option b is correct.

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