Question

A company claims that its new drug is effective is lowering blood pressure. To test this claim, an independent clinic tested the drug on 6 volunteers. Below are the blood pressures before and after taking the new drug.

BP Before Drug	142	130	145	129	138	126
BP After Drug	120	110	140	115	125	110

(a) What tailed test is this? (i.e., RIGHT, LEFT, or TWO-TAILED?)

(b) What is the value of the "Test Statistic"?   

(c) What is the critical value(s)? Use α=0.05.

(d) What is the P-value?

(e) Do you "Reject" or "Fail to Reject" the Null Hypothesis?

(f) Is the company justified in its claim? [Use the Summary Table provided in class]

Answer 1

Answer a)

We are taking difference as Before Drug - After Drug. Since new drug lowers the blood pressure so mean difference should be greater than zero. Thus, it is a RIGHT, tailed test.

Answer b)

The following table is obtained:

The value of the "Test Statistic" is 6.124

Answer c)

The degrees of freedom = n-1 = 6-1 = 5

α = 0.05

The critical t value corresponding to α = 0.05 and df = 5 for a right tailed test is obtained using calculator. Screenshot below:

The critical value is 2.015.

Answer d)

P-value corresponding to Test Statistic t = 6.124 and df = 5 for a right tailed test is obtained using calculator. Screenshot below:

Thus, p-value = 0.0008

Answer e)

Since p-value = 0.0008 < α = 0.05, we reject null hypothesis.

Answer f)

At 0.05 significance level, the company is justified in its claim that its new drug is effective is lowering blood pressure.