A mail order company has 8% success rate. If it mails advertisements to 600 people, find the probability of getting less than 40 sales.

Answer 1

Find mean and standard deviation.

mean = np = 600 * .08 = ?

standard deviation = √npq = √(600)(.08)(.92) = ?

Note: q = 1 - p

I'll let you finish the calculations.

Once you have the mean and standard deviation, then use z-scores:

z = (x - mean)/sd
x = 40

Once you calculate the z-score, use the z-table to find your probability. (Remember that the question is asking for the probability of "getting less than 40" sales.)

I hope this will help get you started.

Answer 2

.1075