Question

Repair Shop Charges. Most automobile repair shops now charge according to a schedule that is claimed to be based on average times required for making a repair. This means that instead of determining the actual time to make a repair and multiplying this value by their hourly rate, repair shops determine the cost from a schedule that is calculated from average times. A critic of this policy is examining how closely this schedule adheres to the actual time to complete a job. The critic first selected a job that is scheduled to take 90 minutes. Next, he takes a random sample of 20 jobs that should take 90 minutes and records the actual time it took to complete the job. Can we infer that the time specified by the schedule is greater than the actual time?

What is (are) the parameter(s) of interest? Choose one of the following symbols (m (the mean of one sample); m_D (the mean difference of two paired (dependent) samples); m₁ - m₂ (the mean difference of two independent samples) and describe the parameter in context of this question in one sentence.

Depending on your answer to part (i), construct one or two relative frequency histograms. Remember to properly title and label the graph(s). Copy and paste these graphs into your document.

Describe the shape of the histogram(s) in one sentence.

Depending on your answer to part (i), construct one or two boxplots and copy and paste these graphs into your document.

Does the boxplot (or do the boxplots) show any outliers? Answer this question in one sentence and identify any outliers if they are present.

Considering the answers provided in parts (iii) and (v), is inference appropriate in this case? Why or why not? Defend your answer using the graphs in two to three sentences.

Actual Time 64 70 80 62 65 67 69 71 68 64 64 75 67 79 70 79 73 58

Answer 1