According to the latest financial reports from a sporting goods store, the mean sales per customer was $75 with a population standard deviation of $6. The store manager believes 39 randomly selected customers spent more per transaction. What is the probability that the sample mean of sales per customer is between $76 and $77 dollars?
mean:
standard deviation:
P(76< X < 77)=
Solution :
Given that ,
mean = = $75
standard deviation = =$6
= / n = 6 / 39 = 0.9608
= P[(76 - 75) /0.9608 < ( - ) / < (77 - 75) / 0.9608)]
= P(1.04 < Z < 2.08)
= P(Z < 2.08) - P(Z < 1.04)
= 0.9812 - 0.8508
= 0.1304
P(76 < X < 77) = 0.1304
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