In a study of heart surgery, one tested the effect of drugs called beta-blockers

Question

In a study of heart surgery, one tested the effect of drugs called beta-blockers on the pulse of patients during surgery. Thirty available subjects received a beta blocker and the pulse rate of each patient was recorded during a critical point during the procedure. The treatment group had a mean pulse rate of 65.2 beats per second and a sample standard deviation of s=7.8. Patients without the beta-blocker have a known average pulse rate of 69.2 during the same critical point of surgery.

a. t-value = -2.8088

b. t-value = -0.5213

c. t-value = 0.5213

d. t-value = 2.8088

In a study of heart surgery, one tested the effect of drugs called beta-blockers on the pulse of patients during surgery. Thirt available subjects received a beta blocker and the pulse rate of each patient was recorded during a critical point during the procedure. The treatment group had a mean pulse rate of 65.2 beats per second and a sample standard deviation of s=7.8. Patients without the beta-blocker have a known average pulse rate of 69.2 during the same critical point of surgery.

We want to test the hypothesis that the mean pulse rate for the treatment group of patients with beta-blockers reduced the known average.

What are the degrees of freedom that should be used for the t-test stated above?

Explanation / Answer

this is left -tailed test as we want to if mean has decreased

df = n-1 =29

t -value = ( 65.2 - 69.2)/(s/sqrt(n) = -4/(7.8/sqrt(30))

= -2.80883

option A) is correct

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