Question

For a test of population proportion H0: p = 0.6 versus Ha: p ≠0.6 , the test statistic equals 1.21. Find the P-value for this test.

Answer 1

Null and Alternative hypothesis:

Ho: p = 0.6

versus

Ha: p ≠0.6

This corresponds to two tail Z test for proportion.

Test statistics:

We get a z-score of 1.21 . Because this is a two-sided test, we have to look at the left tail as well as right tail to find the p-value, i.e. we calculate probabilty in both direction: P(|Z|>1.21)= Area on left of -1.21 and on right of 1.21.

P(Z>1.21) in the Z table is computed as follows :

P ( Z>1.21 )=1 − P ( Z<1.21 )

                   =1 − 0.8869

                   =0.1131

Were, P ( Z<1.21 ) computed as

Also, P(Z<-1.21) = P(Z>1.21) = 0.1131

Hence, P-value = 2* 0.1131 = 02262