A concrete mix is being designed to provide adequate compressive strength for co

Question

A concrete mix is being designed to provide adequate compressive strength for concrete blocks. The specification for a particular application calls for the blocks to have a mean compressive strength is greater than 1300 kPa. A sample of 108 blocks is produced and tested. Their mean compressive strength is 1305.21 kPA, their standard deviation is 74.1 kPa. A test is made of (use =0.05)

H0:1300

vs.

HA:>1300

Find

(a) The value of the test statistic.

(b) The critical value is.

(c) Your decision for the hypothesis test:

A. Do Not Reject H0.
B. Reject H0

Explanation / Answer

a) Z statistic = xbar - µ /(s/n)

                 = 1305.21 - 1300 / [74.1/sqrt(108)] = 0.73

b) Z critical = 1.645

c) Here Z statistic < 1.645, So reject H0

option A, Do not reject H0

we conclude that there is no sufficient evidence that the true mean is greater than 1300

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