Question

Suppose the purchases at a local convenience store are normally distributed with a mean of $10.50, and a standard deviation of $2.10.

If 7 customers are randomly selected, what is the probability that the mean purchase amount for these 7 customers is below $8.75?

Answer 1

Solution :

Given that ,

mean = = $10.50

standard deviation = = $2.10

= / n = 2.10 / 7 = 0.7937

P( < $8.75) = P(( - ) / < (8.75 - 10.50) / 0.7937)

= P(z < -2.2049)

= 0.0137

Probability = 0.0137