In Exercises 5–8, use the relatively small number of given bootstrap samples to construct the confidence interval.Seating Choice In a 3M Privacy Filters poll, respondents were asked to identify their favourite seat when they fly, and the results include these responses: window, window, other, other. Letting “window” = 1 and letting “other” = 0, here are ten bootstrap samples for those responses: {0, 0, 0, 0}, {0, 1, 0, 0}, {0, 1, 0, 1}, {0, 0, 1, 0}, {1, 1, 1, 0}, {0, 1, 1, 0}, {1, 0, 0, 1}, {0, 1, 1, 1}, {1, 0, 1, 0}, {1, 0, 0, 1}. Using only the ten given bootstrap samples, construct an 80% confidence interval estimate of the proportion of respondents who indicated their favourite seat is “window.”

Short Answer

Expert verified

The 80% confidence interval estimate of the population proportion of respondents who prefer the window seat is equal to (0.125,0.75).

Step by step solution

01

Given information

10 bootstrap samples of responses on the favourite seat of the respondents when they fly are considered. “Window” is denoted by 1, and “Other” is denoted by 0.

The ten samples are:

{0, 0, 0, 0}, {0, 1, 0, 0}, {0, 1, 0, 1}, {0, 0, 1, 0}, {1, 1, 1, 0}, {0, 1, 1, 0}, {1, 0, 0, 1}, {0, 1, 1, 1}, {1, 0, 1, 0} and {1, 0, 0, 1}.

02

Expression of the confidence intervals

The 80% confidence interval estimate of the population proportion has the following expression:

P10<p<P90

Here, P10denotes the 10th percentile of the sorted sample proportions and P90denotes the 90th percentile of the sorted sample proportions.

03

Find the sample proportion from each bootstrap sample

The following formula of the sample proportion is used to compute the sample proportions of each of the 10 bootstrap samples:

p^=xn

Here, denotes the number of respondents who prefer window seats, and n is the sample size.

The value of n is the same for all samples and is equal to 4.

The sample proportion for the first bootstrap sample is computed below

The number of 1s in the first sample is the value of x1.

p^1=x1n1=04=0

Similarly, the sample proportions of the remaining 9 bootstrap samples are computed.

The following table shows the sample proportions of each of the 10 bootstrap samples:

Sample number

Bootstrap samples

Sample proportion

1

0

0

0

0

0

2

0

1

0

0

0.25

3

0

1

0

1

0.5

4

0

0

1

0

0.25

5

1

1

1

0

0.75

6

0

1

1

0

0.5

7

1

0

0

1

0.5

8

0

1

1

1

0.75

9

1

0

1

0

0.5

10

1

0

0

1

0.5

The following table shows the sorted values of the sample proportions in ascending order:

0

0.25

0.25

0.5

0.5

0.5

0.5

0.5

0.75

0.75

04

Find the percentiles

For finding the percentile, first, compute the value of the locator (L) as follows.

L=k100×n

Here, k is the percentile value, and n is the total number of observations.

a.

For finding the 10th percentile of the sorted values, first, find the value of L.

Here, n is equal to 10, and k is equal to 5.

Thus,

L=k100×n=10100×10=1

As L is a whole number, the value of P10is the sum of the Lthand theL+1th sample proportions divided by 2.

P10=1stsampleproportion+2ndsampleproportion2=0+0.252=0.125

Thus, P10is equal to 0.125.

For finding the 90th percentile, first, find the value of L.

L=k100×n=90100×10=9

As L is a whole number, the value of P90is the sum of the Lthand L+1ththe sample proportions divided by 2.

P90=9thsampleproportion+10thsampleproportion2=0.75+0.752=0.75

Thus, P90is equal to 0.75.

05

Confidence interval estimate of the population proportion

The 80% confidence interval estimate of the population proportion of respondents who prefer the window seat using the bootstrap samples is as follows.

P10<p<P90=0.125<p<0.75

Thus, the 80%confidence intervalestimate of the population proportion of respondents who prefer the window seat is equal to (0.125,0.75).

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