The natural remedy echinacea is reputed to boost the immune system, which will reduce the number P(5 … X … 7)

P(X Ú 5)

P(X Ú 20)

of flu and colds. A 6-month study was undertaken to determine whether the remedy works. From this study, the following probability distribution of the number of respiratory infections per year (X) for echinacea users was produced.

x 0 1 2 3 4 P (x) .45 .31 .17 .06 .01 Find the following probabilities.

a. An echinacea user has more than one infection per year.

b. An echinacea user has no infections per year.

c. An echinacea user has between one and three

(inclusive) infections per year.