QUESTION 1 The grades of the graduating class at Jefferson College are normally

Question

QUESTION 1

The grades of the graduating class at Jefferson College are normally distributed with a mean of 3.17 and a standard deviation of 0.26. If a graduating student is randomly selected, what is the probability that they have a gpa below 2.8?

QUESTION 2

The cost of a flight from Pittsburgh to Orlando is normally distributed with a mean of $279 and a standard deviation of $21. If a flight is randomly selected, what is the probability that the cost is between $270 and $280?

QUESTION 3

The Decadent Desserts cookbook has recipes for desserts. The number of calories per serving for the recipes in the cookbook is normally distributed with a mean of 320 and a standard deviation of 25. If 15 recipes are randomly selected to serve at a reception, what is the probability that the average calories per serving for the sample is over 330?

QUESTION 4

The number of pages in a Biology textbook is normally distributed with a mean of 492 pages and a standard deviation of 30 pages. How many pages would a book have if it is in the shortest 11% of Biology textbooks?

QUESTION 5

If the same data were used to construct 3 confidence intervals, for the mean using different levels of confidence, which one would have the largest margin of error?

90%

95%

99%

They would all be the same.

90%

95%

99%

They would all be the same.

Explanation / Answer

The grades are normally distributed with a mean of 3.17 and a standard deviation of 0.26. z is given as (x-mean)/s

we need P(x<2.8) =P(z<(2.8-3.17)/0.26)=P(z<-1.42) or 1-P(z<1.42) , from normal distribution table we get 1-0.9222=0.0778

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