Pfizer Inc. is the manufacturer of Revolution (Selamectin), a topical parasiticide used for the treatment, control, and prevention of flea infestation, heartworm, and ear mites for dogs and cats. One of its selling points is that it provides protection for an entire month. Such claims are made on the basis of research and statistical studies. The file entitled Fleafree contains data similar to those obtained in Pfizer's research. It presents the number of days Revolution could remain effective when applied to mature cats.

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 number of days Revolution could remain effective.

c. If the marketing department wished to advertise the number of days that 90% of the cats remain protected while using Revolution, what would this number of days be?