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In: Statistics and Probability

Fowle Marketing Research, Inc., bases charges to a client on the assumption that telephone surveys can...

Fowle Marketing Research, Inc., bases charges to a client on the assumption that telephone surveys can be completed in a mean time of 15 minutes or less. If a longer mean survey time is necessary, a premium rate is charged. A sample of 35 surveys provided a mean time of 17 minutes. Based upon past studies, the population standard deviation is assumed known with σ=4. Is the premium rate justified?

What is the critical value, using a = .01 (to 2 decimals)?

Solutions

Expert Solution

Solution :

This a right (One) tailed test.

The null and alternative hypothesis is,  

Ho: 15

Ha: 15

The test statistics,

Z =( - )/ (/n)

= ( 17 - 15 ) / ( 4 / 35 )

= 2.96

Critical value of  the significance level is α = 0.01, and the critical value for a right-tailed test is

= 2.33

Since it is observed that ∣z∣=2.96 > zc=2.33, it is then concluded that the null hypothesis is rejected.

orchestra answered 2 years ago
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