A standardized test has been conducted to compute the compressive strength of two brands of cements. Fourteen cubes of cement 1 were tested by crushing them under a hydraulic press. Fifteen cubes of cement 2 were tested under similar condition. The cubes of cement 1 gave an average compressive strength of 59.4 MPa with a sample standard deviation of 7.8 MPa, while the cubes of cement 2 gave an average of 55.8 MPa with a sample standard deviation of 8.2 MPa. Can we conclude at the 0.05 level of significance that the compressive strength of cement 1 exceeds that of cement 2 by more than 2 MPa? Assume the populations to be approximately normal with equal variances.

1.

What is the statistic/type of hypothesis testing to be used in this problem?

Two Sample Z Test

Two Sample Pooled Variance t Test

Two Sample Separate Variance t Test

Paired t Test

2.

What is the critical value?

1.3137

1.7033

2.4727

2.0518

3.

What is the standardized test statistic?

1.254

2.9766

8.0099

0.5375