Boxes of cereal produced in a given factory are regularly inspected and must contain an average weight of 500 grams. The individual box weights are assumed to follow a normal distribution with a mean of 500 and a standard deviation of 20 grams. In routine inspections, the inspector selects a random sample of 14 cereal boxes and if the average sample weight is below 495 or above 505, the manufacturing process is stopped and the box filling machine is adjusted. a. What is the probability that a box selected at random weighs between 489 and 508 grams?  b.  What is the probability that the average weight of a sample of 14 boxes is between 489 and 508 grams?  c. Do you want to know what is the weight of a box that is exceeded by only 5% of the boxes?

Glencoe Algebra 1, Student Edition, 9780079039897, 0079039898, 2018
18th Edition
ISBN:9780079039897
Author:Carter
Publisher:Carter
Chapter10: Statistics
Section10.4: Distributions Of Data
Problem 19PFA
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Boxes of cereal produced in a given factory are regularly inspected and must contain an average weight of 500 grams. The individual box weights are assumed to follow a normal distribution with a mean of 500 and a standard deviation of 20 grams. In routine inspections, the inspector selects a random sample of 14 cereal boxes and if the average sample weight is below 495 or above 505, the manufacturing process is stopped and the box filling machine is adjusted.

a. What is the probability that a box selected at random weighs between 489 and 508 grams? 
b.  What is the probability that the average weight of a sample of 14 boxes is between 489 and 508 grams? 
c. Do you want to know what is the weight of a box that is exceeded by only 5% of the boxes? 

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