Question

3. A new 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 µ greater than 1350 kPa. A sample of 100 blocks is produced and tested. Their mean compressive strength is 1356 kPa and their standard deviation is 70 kPa.
4. What is the most appropriate null hypothesis regarding the population mean µ. Indicate the alternate hypothesis as well.
5. Find the P-value.

Can you conclude that the blocks meet the specification? Or are you convinced that they do not? Explain your answer.

Answer 1

H0: 1350

Ha: > 1350

Test statistics

t = (- ) / (S / sqrt(n) )

= ( 1356 - 1350) / (70 / sqrt(100) )

= 0.86

df = n - 1 = 100 - 1 = 99

Using T table,

With test statistics of 0.86 and df of 99,

p-value = 0.1959

Since p-value > 0.05 level, do not reject H0.

We conclude that we do not have sufficient evidence to support the claim that the blocks

meet the specification