A report states that the cost of repairing a hybrid vehicle is falling even whil

Question

A report states that the cost of repairing a hybrid vehicle is falling even while typical repairs on conventional vehicles are getting more expensive. The most common hybrid? repair, replacing the hybrid inverter? assembly, had a mean repair cost of ?$3927 in 2012. Industry experts suspect that the cost will continue to decrease given the increase in the number of technicians who have gained expertise on fixing? gas-electric engines in recent months. Suppose a sample of 100 hybrid inverter assembly repairs completed in the last month was selected. The sample mean repair cost was $3860 with the sample standard deviation of $600.

a. Is there evidence that the population mean cost is less than $3,927? (Use a 0.01 level of significance.) State the null and alternative hypotheses. Ho: 2 $ 3927 H1:

Explanation / Answer

Here you need to TINV function of excel as follows:

=TINV( 0.01*2, 99)

It gives you 2.364605852.

First argument in the function is level of significance multiplied by 2. And second argument is degreeof freedom df=n-1.

TINV function by default gives two tailed critical value so for one tailed we have to multiplied level of siginificnace by 2.

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