Posted by **johnny** on Tuesday, November 27, 2012 at 9:38pm.

The Ledd Pipe Company has received a large shipment of pipes, and a quality control inspector wishes to

estimate the average diameter of these pipes. A random sample of 18 pipes produces an average diameter of

2.56 mm with a standard deviation of 0.05 mm.

The average diameter of the pipes must not differ significantly from 2.52 mm. Is there enough evidence at

the 5% level of significance to conclude that the true average diameter differs from this amount? Conduct an

appropriate hypothesis test using (i) the p-value method, (ii) the rejection point method, and (iii) the confidence

interval method.

- stats -
**RD Statistics**, Wednesday, November 28, 2012 at 1:36am
n = 18

xbar = 2.56 s = 0.05

H0 : mu = 2.52 H1: mu not equal 2.52

test stat = t = (xbar-mu)/(s/sqrt(n)) = 3.39

p-value = 0.003 < 0.05 Reject H0

t-critical = 2.11 < 3.39 Reject H0

CI =(xbar-t-critical*s/sqrt(n), xbar+t-critical*s/sqrt(n))

(2.54, 2.58)

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