Question

1. A cigarette manufacturer claims that one-eighth of the US adult population smokes cigarettes. In a random sample of 100 adults, 5 are cigarette smokers. Test the manufacturer's claim at alpha= 0.05.  (critical values of z are ± 1.96).

2. A local telephone company claims that the average length of a phone call is 8 minutes. In a random sample of 58 phone calls, the sample mean was 7.8 minutes and the standard deviation was 0.5 minutes. Is there enough evidence to support this claim at alpha= 0.05? (critical values of z are ± 1.96).

Answer 1

1)

Given:

P = 1/8 = 0.125,

Q =1-P = 1-0.125 = 0.875, n= 100,

Hypothesis:

(Claim)

Test statistic:

Conclusion:

| Test statistic (Z) | > Critical value, i.e. 2.27 > 1.96, That is Reject Ho at 5% level of signficance.

Ho is Rejected; you should conclude. " there is sufficient evidence to indicate that the manufactures claim is false."