Question

The strength of one's immune system can be evaluated in several ways. One of the most popular methods involves measuring the concentration of adenosine triphosphate (ATP) in the blood. In women, the mean blood ATP level is 390 ng/mL, and the standard deviation is 115 ng/mL. It has been hypothesized that women with Major Depressive Disorder (MDD) have decreased immune function. A recent study found that a random sample of 70 women with MDD had an average blood ATP level of 355 ng/mL. Using a one-sample z test, what is the p-value of this result? (HINT: This involves a one-tailed hypothesis test.)

Answer 1

H0: Null Hypothesis: = 390

HA: Alternative Hypothesis: < 390

n = 70

= 355

= 115

SE = /

=115/ = 13.7451

Test statistic is:

Z = (355 - 390)/13.7451 = - 2.55

Table of Area Under Standard Normal Curve gives area = 0.4946

So,

P - Value = 0.5 - 0.4946 = 0.0054

So,

Answer is:

0.0054