17. Explaining confidence A 95%confidence interval for the mean body mass index (BMI)of young American women is 26.8±0.6. Discuss whether each of the following explanations is correct.
(a) We are confident that 95%of all young women have BMIbetween 26.2and 27.4.
(b) We are 95%confident that future samples of young women will have mean BMIbetween 26.2and 27.4.
(c) Any value from 26.2to 27.4is believable as the true mean BMI of young American women.
(d) In 95%of all possible samples, the population mean BMIwill be between 26.2and 27.4.
(e) The mean BMIof young American women cannot be 28.

Short Answer

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(a) The explanation that 95%confident of all young women have mean BMIbetween 26.2and 27.4is incorrect.

(b) The explanation that 95%confident that future samples of young women will have mean BMIbetween 26.2and 27.4is incorrect.

(c) The explanation that any value from 26.2to 27.4is believable as the true mean BMIof young American women is correct.

(d) The explanation that in 95%of all possible samples, the population mean BMIwill be between 26.2and 27.4is incorrect.

(e) The explanation that the mean BMIof young American women cannot be 28 is incorrect.

Step by step solution

01

Part (a) Step 1: Given information

To determine whether the statement that 95%of all young women have BMIbetween26.2and 27.4is correct or not.

02

Part (a) Step 2: Explanation

Let, the Confidence interval is 95%
And the body mass index as:

(BMI)=26±0.6
Also, 26.2and 27.4
The confidence interval is only stated for young women in this observation, not for individual women.
As a result, explanation (a) is incorrect.

03

Part(b) Step 1: Given information

To determine whether the statement that 95%confident that future samples of young women will have mean BMIbetween 26.2and 27.4is correct or not.

04

Part (b) Step 2: Explanation

Let, the confidence interval is 95%.

And the body mass index is (BMI)=26±0.6
Also,

26.2 and 27.4.
Because the confidence intervals for future samples may differ.
It's impossible to predict where the true mean BMIwill fall between 26.2 and 27.4.
As a result, explanation (b) is incorrect

05

Part (c) Step 1: Given information

To determine whether the statement that any value from 26.2to 27.4is believable as the true mean BMIof young American women is correct or not.

06

Part (c) Step 2: Explanation

Let the confidence interval is 95%.

And the body mass index is (BMI)=26±0.6
Also,26.2and 27.4.
The true mean BMIranges from 26.2to 27.4.
As a result, any value between 26.2and 27.4might be considered reasonable as the genuine mean BMI.
As a result, the explanation is correct.

07

Part (d) Step 1: Given information

To determine whether the statement that in 95%of all possible samples, the population mean BMIwill be between 26.2and 27.4is correct or not.

08

Part (d) Step 2: Explanation

Let, the confidence interval is95%.

And the body mass index is (BMI)=26±0.6
Also,

26.2and 27.4.

The true mean BMIlies between the intervals 26.2and 27.4in the 95 percent confidence interval.
The genuine mean BMIis not present in the remaining 5 percent samples.
As a result, explanation is incorrect.

09

Part(e) Step 1: Given information

To determine whether the statement that the mean BMIof young American women cannot be 28is correct or not.

10

Part (e) Step 2: Explanation

Let, the confidence interval is 95%.

And the Body mass index is (BMI)=26±0.6
26.2and 27.4
The population mean is unknown in this explanation. As a result, the average BMI may not be equal to 28.
As a result, explanation (e) is incorrect.

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Most popular questions from this chapter

Hallux abducto valgus (call it HAV) is a deformation of the big toe that is fairly uncommon in youth and often requires surgery. Doctors used X-rays to measure the angle (in degrees) of deformity in a random sample of patients under the age of 21who came to a medical center for surgery to correct HAV. The angle is a measure of the seriousness of the deformity. For these 21patients, the mean HAV angle was 24.76degrees and the standard deviation was 6.34degrees. A dot plot of the data revealed no outliers or strong skewness.

(a) Construct and interpret a 90%confidence interval for the mean HAV angle in the population of all such patients.

(b) Researchers omitted one patient with an HAV angle of 50degrees from the analysis due to a measurement issue. What effect would including this outlier have on the confidence interval in (a)? Justify your answer.

You have measured the systolic blood pressure of an SRS of 25company employees. A 95%confidence interval for the mean systolic blood pressure for the employees of this company is (122,138). Which of the following statements gives a valid interpretation of this interval?

(a) 95%of the sample employees have systolic blood pressure between 122and138.

(b) 95%of the population of employees have systolic blood pressure between 122and138.

(c) If the procedure were repeated many times, 95%of the resulting confidence intervals would contain the population mean systolic blood pressure.

(d) The probability that the population mean blood pressure is between 122and138is 0.95.

(e) If the procedure were repeated many times, 95%of the sample means would be between122and138.

Many television viewers express doubts about the validity of certain commercials. In an attempt to answer their critics, Timex Group USA wishes to estimate the proportion of consumers who believe what is shown in Timex television commercials. Let prepresent the true proportion of consumers who believe what is shown in Timex television commercials. What is the smallest number of consumers that Timex can survey to guarantee a margin of error of 0.05or less at a 99%confidence level?

(a) 550

(b) 600

(c) 650

(d) 700

(c)750

It’s critical Find the appropriate critical value for constructing a confidence interval in each of the following settings.

(a) Estimating a population proportion p at a 94%confidence level based on an SRS of size 125.

(b) Estimating a population mean M at a 99%confidence level based on an SRS of size 58.

Alcohol abuse has been described by college presidents as the number one problem on campus, and it is an important cause of death in young adults. How common is it? A survey of 10,904 randomly selected U.S. college students collected information on drinking behavior and alcohol-related problems." The researchers defined "frequent binge drinking" as having five or more drinks in row three or more times in the past two weeks. According to this definition, 2486 students were classified as frequent binge drinkers.

1. Identify the population and the parameter of interest.

2. Check conditions for constructing a confidence interval for the parameter.

3. Find the critical value for a 99 \% confidence interval. Show your method. Then calculate the interval.

4. Interpret the interval in context.

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