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Chapter 7: Q. 7.7 (page 408)

The mean number of minutes for app engagement by a tablet use in 8.2minutes. Suppose the standard deviation is one minute . Take a sample size of 70.

a. What is probability of that the sum of the sample is between seven hours and ten hours? What does this mean in context of the problem ?

b. Find the 84thand 16thpercentiles for the sum of the sample. interprets these values in context.

Short Answer

Expert verified

The value ofa=2

Step by step solution

01

Part (a) Step 1: Given Information

We have given that the app engagement by a tablet use in 8.2minutes.

we need to find the probability of that the sample is between seven hours and ten hours and 84thand16thpercentiles.

02

Part (a) Step 2: Simplify

We must find the sum of the sample between 7h(420min)and 10h(600min)

P(420<∑x<600)=normalcdf (420,600,574,8.37)=0.9991

Or

Pr(420∑x<600)=Pr420-5748.37<Z<600-5748.37=Pr(-18.399<Z3.1063)=Pr(Z<3.1063)-Pr(Z<-18.399)=0.991-0=0.9991

Normal distribution:Pr(420<x<600)=0.9991

03

Part (b) Step 3: Calculation

Let k1=the 84thpercentile.

k1=invNorm(0.84,574,8.37)=582.3236

Let k2=the 16thpercentile.

K2=invNorm(0.16,574,8.37)=565.6764

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Most popular questions from this chapter

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