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Confidence Interval for Hemoglobin Large samples of women and men are obtained, and the hemoglobin level is measured in each subject. Here is the \(95 \%\) confidence interval for the difference between the two population means, where the measures from women correspond to population 1 and the measures from men correspond to population 2 : \(-1.76 \mathrm{g} / \mathrm{dL}<\mu_{1}-\mu_{2}<-1.62 \mathrm{g} / \mathrm{dL}\) a. What does the confidence interval suggest about equality of the mean hemoglobin level in women and the mean hemoglobin level in men? b. Write a brief statement that interprets that confidence interval. c. Express the confidence interval with measures from men being population 1 and measures from women being population 2

Short Answer

Expert verified
a. The mean hemoglobin level in women is less than that in men.b. Women’s mean hemoglobin level is 1.62 to 1.76 g/dL lower than men’s.c. \(1.62 < \mu_{2} - \mu_{1} < 1.76\) g/dL

Step by step solution

01

Understanding the Confidence Interval (Part a)

The confidence interval given is \[-1.76 \text{ g/dL} < \mu_{1} - \mu_{2} < -1.62 \text{ g/dL} \]Since both bounds of the interval are negative, it suggests that the mean hemoglobin level in women (population 1) is less than that in men (population 2). If the interval contained zero, it would suggest that the means might be equal, but here zero is not in the interval.
02

Interpreting the Confidence Interval (Part b)

The confidence interval means that we are \(95\%\) confident that the true difference in mean hemoglobin levels between women and men lies between \[-1.76 \text{ g/dL} \text{ and } -1.62 \text{ g/dL} \]In simpler terms, women are expected to have a mean hemoglobin level that is between 1.62 g/dL to 1.76 g/dL lower than that of men.
03

Reversing Population Measures (Part c)

When switching the populations, where measures from men correspond to population 1 and measures from women correspond to population 2, the confidence interval for \[ \mu_{2} - \mu_{1} \] becomes: \[ 1.62 \text{ g/dL} < \mu_{2} - \mu_{1} < 1.76 \text{ g/dL} \]. This reflects the same difference in means, but with the direction reversed.

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Key Concepts

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

95% confidence interval
A 95% confidence interval provides a range of values within which we expect the true population parameter to fall, with 95% certainty. In other words, if we were to take 100 different samples and construct a confidence interval from each, we would expect 95 of those intervals to contain the true population parameter.
For example, consider the interval \[-1.76 \text{ g/dL} < \mu_{1} - \mu_{2} < -1.62 \text{ g/dL}\]. This interval tells us that we are 95% confident that the true difference in mean hemoglobin levels between women and men falls between -1.76 g/dL and -1.62 g/dL. Since zero is not in this interval, it suggests a significant difference between the two population means.
Mean difference
The mean difference is the difference between the average values of a particular measurement in two different groups. This statistic is used to compare the central tendency of two groups.
In this exercise, we calculated the mean difference in hemoglobin levels between women and men. If we denote the mean hemoglobin level for women as \mu_{1}\ and for men as \mu_{2}\, the difference is represented by \mu_{1} - \mu_{2}\. The negative values of our confidence interval indicate that the mean hemoglobin level for women is lower than that for men.
A different way to express this is by reversing the populations and taking the difference in the opposite direction. Changing the order to \mu_{2} - \mu_{1}\ gives a positive interval \[1.62 \text{ g/dL} < \mu_{2} - \mu_{1} < 1.76 \text{ g/dL}\], showing men have a higher mean hemoglobin level.
Hemoglobin levels
Hemoglobin is a protein in red blood cells that carries oxygen throughout the body. It's a crucial factor in determining an individual's overall health and oxygenation capacity.
Hemoglobin levels can vary between populations due to numerous factors including gender, age, and health status. In this exercise, hemoglobin levels were measured for large samples of both women and men. Understanding the distribution of these levels in different populations helps in medical assessments and research.
When analyzing these levels statistically, we are often interested in mean values and differences between groups, as these can provide insight into potential physiological differences or health disparities.
Population comparison
Population comparison involves comparing statistical measures (like means, medians, proportions) between two or more distinct groups. This is useful in understanding differences and similarities across different groups.
In the given exercise, we compare hemoglobin levels between women and men. We use a confidence interval to make inferences about the true difference in mean hemoglobin levels between these two groups.
The process involves:
  • Gathering large sample sizes from each population to ensure reliability.
  • Calculating the mean hemoglobin level for each group.
  • Constructing a confidence interval to provide a range within which the true mean difference lies.
In our example, the interval \[-1.76 \text{ g/dL} < \mu_{1} - \mu_{2} < -1.62 \text{ g/dL}\] indicates that women, on average, have lower hemoglobin levels compared to men. This interval provides a statistically significant difference by not including zero.

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Most popular questions from this chapter

Assume that the two samples are independent simple random samples selected from normally distributed populations, and do not assume that the population standard deviations are equal. (Note: Answers in Appendix D include technology answers based on Formula 9 - 1 along with "Table" answers based on Table \(A\) - 3 with df equal to the smaller of \(\boldsymbol{n}_{I}-\boldsymbol{I}\) and \(\boldsymbol{n}_{2}-\boldsymbol{I} .\) ) Second-Hand Smoke Data Set 12 "Passive and Active Smoke" in Appendix B includes cotinine levels measured in a group of nonsmokers exposed to tobacco smoke \((n=40,\) \(\bar{x}=60.58 \mathrm{ng} / \mathrm{mL}, s=138.08 \mathrm{ng} / \mathrm{mL})\) and a group of nonsmokers not exposed to tobacco smoke \((n=40, \bar{x}=16.35 \mathrm{ng} / \mathrm{mL}, s=62.53 \mathrm{ng} / \mathrm{mL}) .\) Cotinine is a metabolite of nicotine, meaning that when nicotine is absorbed by the body, cotinine is produced. a. Use a 0.05 significance level to test the claim that nonsmokers exposed to tobacco smoke have a higher mean cotinine level than nonsmokers not exposed to tobacco smoke. b. Construct the confidence interval appropriate for the hypothesis test in part (a). c. What do you conclude about the effects of second-hand smoke?

Use the listed paired sample data, and assume that the samples are simple random samples and that the differences have a distribution that is approximately normal. Listed below are brain volumes (cm \(^{3}\) ) of twins from Data Set 8 "IQ and Brain Size" in Appendix B. Construct a \(99 \%\) confidence interval estimate of the mean of the differences between brain volumes for the first-born and the second-born twins. What does the confidence interval suggest? $$\begin{array}{l|r|r|r|r|r|r|r|r|r|r} \hline \text { First Born } & 1005 & 1035 & 1281 & 1051 & 1034 & 1079 & 1104 & 1439 & 1029 & 1160 \\ \hline \text { Second Born } & 963 & 1027 & 1272 & 1079 & 1070 & 1173 & 1067 & 1347 & 1100 & 1204 \\ \hline \end{array}$$

Assume that the two samples are independent simple random samples selected from normally distributed populations, and do not assume that the population standard deviations are equal. (Note: Answers in Appendix D include technology answers based on Formula 9 - 1 along with "Table" answers based on Table \(A\) - 3 with df equal to the smaller of \(\boldsymbol{n}_{I}-\boldsymbol{I}\) and \(\boldsymbol{n}_{2}-\boldsymbol{I} .\) ) Regular Coke and Diet Coke Data Set 26 "Cola Weights and Volumes" in Appendix B includes weights (b) of the contents of cans of Diet Coke \((n=36, \bar{x}=0.78479 \text { lb, } s=0.00439\) lb) and of the contents of cans of regular Coke \((n=36, \bar{x}=0.81682 \mathrm{lb}, s=0.00751 \mathrm{lb})\) a. Use a 0.05 significance level to test the claim that the contents of cans of Diet Coke have weights with a mean that is less than the mean for regular Coke. b. Construct the confidence interval appropriate for the hypothesis test in part (a). c. Can you explain why cans of Diet Coke would weigh less than cans of regular Coke?

Use the listed paired sample data, and assume that the samples are simple random samples and that the differences have a distribution that is approximately normal. Researchers collected data on the numbers of hospital admissions resulting from motor vehicle crashes, and results are given below for Fridays on the 6 th of a month and Fridays on the following 13 th of the same month (based on data from "Is Friday the 13 th Bad for Your Health?" by Scanlon et al., British Medical Journal, Vol. \(307,\) as listed in the Data and Story Line online resource of data sets). Construct a \(95 \%\) confidence interval estimate of the mean of the population of differences between hospital admissions on days that are Friday the 6 th of a month and days that are Friday the 13 th of a month. Use the confidence interval to test the claim that when the 13 th day of a month falls on a Friday, the numbers of hospital admissions from motor vehicle crashes are not affected. $$\begin{array}{|l|c|c|c|c|c|c|} \hline \text { Friday the 6th } & 9 & 6 & 11 & 11 & 3 & 5 \\ \hline \text { Friday the 13th } & 13 & 12 & 14 & 10 & 4 & 12 \\ \hline \end{array}$$

Test the given claim. Identify the null hypothesis, alternative hypothesis, test statistic, P-value or critical value(s), then state the conclusion about the null hypothesis, as well as the final conclusion that addresses the original claim. A study investigated survival rates for in-hospital patients who suffered cardiac arrest. Among 58,593 patients who had cardiac arrest during the day, 11,604 survived and were discharged. Among 28,155 patients who suffered cardiac arrest at night, 4139 survived and were discharged (based on data from "Survival from In-Hospital Cardiac Arrest During Nights and Weekends," by Peberdy et al., Joumal of the American Medical Association, Vol. 299, No. 7). We want to use a 0.01 significance level to test the claim that the survival rates are the same for day and night. a. Test the claim using a hypothesis test. b. Test the claim by constructing an appropriate confidence interval. c. Based on the results, does it appear that for in-hospital patients who suffer cardiac arrest, the survival rate is the same for day and night?

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