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

Short Answer

Expert verified
(a), (b), (d), and (e) are incorrect; (c) is correct.

Step by step solution

01

Understanding Confidence Interval Basics

A confidence interval provides a range within which we can be fairly certain the population parameter lies. In this case, the 95% confidence interval for the mean BMI is from 26.2 to 27.4.
02

Analyzing Statement (a)

This statement is incorrect because a confidence interval applies to the population mean, not percentages of individuals. The interval does not imply that 95% of individuals fall within this range.
03

Analyzing Statement (b)

This statement is incorrect. The 95% confidence interval is for the true mean BMI of the population, not future sample means.
04

Analyzing Statement (c)

This statement is correct. The interval from 26.2 to 27.4 represents the plausible range for the true mean BMI of young American women based on the sample data.
05

Analyzing Statement (d)

This statement is incorrect. The population mean is a fixed value, and the confidence interval represents ranges that would capture this fixed mean in 95% of samples if we repeated the sampling process many times.
06

Analyzing Statement (e)

This statement is incorrect. While less likely, a mean BMI of 28 is still possible but outside most confidence interval estimates when using this data; it can't be completely ruled out.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Body Mass Index (BMI)
The Body Mass Index (BMI) is a numerical measure used to evaluate an individual's body fat based on their weight relative to their height. BMI is calculated by dividing a person's weight in kilograms by the square of their height in meters: \[ BMI = \frac{weight\ (kg)}{height^2\ (m^2)} \]
This simple formula provides a useful approximation for assessing whether a person is underweight, normal weight, overweight, or obese.
For young American women, the discussion often involves understanding what constitutes a normal or healthy BMI range. In many studies, a BMI between 18.5 and 24.9 is considered normal. Values above this can indicate overweight (25-29.9) or obesity (30 and above).
Why is BMI important? Primarily because it helps in identifying potential health risks associated with excessive body fat, such as heart disease, diabetes, and hypertension. When analyzing BMI data, statisticians use it to draw conclusions about the health trends in a population, which makes the interpretation of confidence intervals in this context very relevant.
Population Parameter
A population parameter is a characteristic or measure of an entire population. In statistical studies, it is often impossible to measure the entire population due to its size. Therefore, researchers take a sample and then draw inferences about the population parameter.
The mean BMI of young American women is an example of a population parameter. While we aim to find this true mean, measuring it directly is challenging. Therefore, statisticians create confidence intervals to estimate this parameter.
Understanding population parameters is crucial in fields such as public health, economics, and any domain involving large datasets. It allows statisticians to provide estimates and predictions that can guide decision-making, policy changes, and future research. Knowing the true value of a population parameter can inform strategies to mitigate risks and improve overall well-being.
Sampling Interpretation
Sampling interpretation involves understanding how information from a sample can represent the larger population. It is important because we rarely collect data from the entire population.
A key part of sampling interpretation is understanding the concept of a confidence interval. When we say a 95% confidence interval for the mean BMI is 26.8 卤 0.6, it means if we were to take numerous samples and calculate a confidence interval from each, 95% of those intervals would contain the true population mean.
However, this interpretation does not imply that 95% of individual young American women have a BMI within this range. That's a common misconception. Instead, it shows the reliability of our estimate regarding the population mean. Sampling interpretation helps to deal with the variability inherent in any sampling process, giving a more accurate representation of the population.
Statistical Analysis
Statistical analysis is the process of collecting and analyzing data to identify trends, patterns, and relationships within a dataset. It is a foundational element in understanding phenomena across various fields.
When conducting statistical analyses, concepts like confidence intervals are vital. These intervals help in understanding the precision of an estimate鈥攊n this case, the mean BMI. It guides researchers in knowing how much trust they can place in their derived estimates.
Understanding statistical analysis also involves recognizing the limitations and assumptions made during the process. For instance, while confidence intervals give a range for estimated values, they assume a normal distribution and that the sample is a fair representation of the population.
Statistical analysis can be used to test hypotheses, draw conclusions, and make predictions. It is crucial in both academic research and practical applications, such as policy development and business strategy.

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Most popular questions from this chapter

Multiple choice: Select the best answer for Exercises 21 to 24. You have measured the systolic blood pressure of an SRS of 25 company 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 of employees have a systolic blood pressure between 122 and 138. (b) 95% of the population of employees have a systolic blood pressure between 122 and 138. (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 122 and 138 is 0.95. (e) If the procedure were repeated many times, 95% of the sample means would be between 122 and 138.

Critical values What critical value t* from Table B should be used for a confidence interval for the population mean in each of the following situations? (a) A 90% confidence interval based on n 12 observations. (b) A 95% confidence interval from an SRS of 30 observations.

Multiple choice: Select the best answer for Exercises 75 to 78. One reason for using a t distribution instead of the standard Normal curve to find critical values when calculating a level C confidence interval for a population mean is that (a) z can be used only for large samples. (b) z requires that you know the population standard deviation S. (c) z requires that you can regard your data as an SRS from the population. (d) the standard Normal table doesn鈥檛 include confidence levels at the bottom. (e) a z critical value will lead to a wider interval than a t critical value.

Gambling and the NCAA Gambling is an issue of great concern to those involved in college athletics. Because of this concern, the National Collegiate Athletic Association (NCAA) surveyed randomly selected student-athletes concerning their gambling-related behaviors. \(^{17}\) Of the 5594 Division I male athletes in the survey, 3547 reported participation in some gambling behavior. This includes playing cards, betting on games of skill, buying lottery tickets, betting on sports, and similar activities. A report of this study cited a 1% margin of error. (a) The confidence level was not stated in the report. Use what you have learned to find the confidence level, assuming that the NCAA took an SRS. (b) The study was designed to protect the anonymity of the student-athletes who responded. As a result, it was not possible to calculate the number of students who were asked to respond but did not. How does this fact affect the way that you interpret the results?

2K10 begins In January 2010, a Gallup Poll asked a random sample of adults, 鈥淚n general, are you satisfied or dissatisfied with the way things are going in the United States at this time?鈥 In all, 256 said that they were satisfied and the remaining 769 said they were not. Construct and interpret a 90% confidence interval for the proportion of adults who are satisfied with how things are going. Follow the four-step process.

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