Question: Fiber Systems makes boat tops for a number of boat manufacturers. Its fabric has a limited two-year warranty. Periodic testing is done to determine if the warranty policy should be changed. One such study may have examined those covers that became unserviceable while still under warranty. Data that could be produced by such a study are contained in the file titled Covers. The data represent assessment of the number of months a cover was used until it became unserviceable.
a. Produce a frequency distribution for these data. Convert the frequency distribution into a probability distribution using the relative frequency assessment method.
b. Calculate the expected value and standard deviation for the time until the covers became unserviceable.
c. The quality-control department thinks that among those covers that do become unserviceable while still under warranty, the majority last longer than 19 months. Produce the relevant statistic to verify this assumption.