Question

A mail order company has a 7% success rate. If it mails advertisements to 646 people, find the probability of getting less than 40 sales. Roundz-value calculators to 2 decimal places and final answer to 4 decimal places.

Answer 1

Solution :

Given that,

p = 0.07

q = 1 - p = 1 - 0.07 = 0.93

n = 646

Using binomial distribution,

Mean = = n * p = 646 * 0.07 = 45.22

Standard deviation = = n * p * q = 646 * 0.07 * 0.93 = 6.48

P(x < 40) = P[(x - ) / < (40 - 45.22) / 6.48]

= P(z < -0.81)

Using z table,

= 0.2090