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Elementary Statistics 8th Edition Neil A. Weiss - Solutions

x1 = 20, s1 = 4, n1 = 10, . x2 = 18, s2 = 5, n2 = 15 a. Right-tailed test, α = 0.05 b. 90% confidence intervalWe have provided summary statistics for independent simple random samples from two populations. In each case, use the nonpooled t-test and the nonpooled t-interval procedure to conduct the
x1 = 20, s1 = 4, n1 = 10, . x2 = 23, s2 = 5, n2 = 15a. Left-tailed test, α = 0.05 b. 90% confidence intervalWe have provided summary statistics for independent simple random samples from two populations. In each case, use the nonpooled t-test and the nonpooled t-interval procedure to conduct the
x1 = 20, s1 = 6, n1 = 20, . x2 = 24, s2 = 2, n2 = 15a. Left-tailed test, α = 0.05 b. 90% confidence intervalWe have provided summary statistics for independent simple random samples from two populations. In each case, use the nonpooled t-test and the nonpooled t-interval procedure to conduct the
x1 = 20, s1 = 2, n1 = 30, x2 = 18, s2 = 5, n2 = 40a. Right-tailed test, α = 0.05 b. 90% confidence intervalWe have provided summary statistics for independent simple random samples from two populations. In each case, use the nonpooled t-test and the nonpooled t-interval procedure to conduct the
According to the American Psychiatric Association, posttraumatic stress disorder (PTSD) is a common psychological consequence of traumatic events that involve a threat to life or physical integrity. During the Cold War, some 200,000 people in East Germany were imprisoned for political reasons. Many
The seagrass Thalassia testudinum is an integral part of the Texas coastal ecosystem. Essential to the growth of T. testudinum is ammonium. Researchers K. Lee and K. Dunton of the Marine Science Institute of the University of Texas at Austin noticed that the sea grass beds in Corpus Christi Bay
Refer to Example 10.6 on page 411. The researchers also obtained the following data on the number of acute postoperative days in the hospital using the dynamic and static systems.At the 5% significance level, do the data provide sufficient evidence to conclude that the mean number of acute
Frustrated passengers, congested streets, time schedules, and air and noise pollution are just some of the physical and social pressures that lead many urban bus drivers to retire prematurely with disabilities such as coronary heart disease and stomach disorders. An intervention program designed by
Previous research has suggested that changes in the activity of dopamine, a neurotransmitter in the brain, may be a causative factor for schizophrenia.In the paper "Schizophrenia: Dopamine Î²-Hydroxylase Activity and Treatment Response" (Science, Vol. 216, pp. 1423-1425), D. Sternberg et al.
D. Cristol et al. published results of their studies of two subspecies of dark-eyed juncos in the article "Migratory Dark-Eyed Juncos, Junco Hyemalis, haveBetter Spatial Memory and Denser Hippocampal Neurons than Nonmigratory Conspecifics" (Animal Behaviour, Vol. 66, pp. 317-328). One of the
Refer to Exercise 10.71 and obtain a 90% confidence interval for the difference, μ1 − μ2, between the mean ages at arrest of East German prisoners with chronic PTSD and remitted PTSD.
Refer to Exercise 10.72 and determine a 98% confidence interval for the difference, μ1 − μ2, between the mean sediment ammonium concentrations in CCB and LLM.
Refer to Exercise 10.73 and find a 90% confidence interval for the difference between the mean numbers of acute postoperative days in the hospital with the dynamic and static systems.
Refer to Exercise 10.74 and find a 90% confidence interval for the difference between the mean heart rates of urban bus drivers in Stockholm in the two environments.
Refer to Exercise 10.75 and determine a 98% confidence interval for the difference between the mean dopamine activities of psychotic and nonpsychotic patients.
Refer to Exercise 10.76 and find a 99% confidence interval for the difference between the mean wing lengths of the two subspecies.
In the article "Sleep Apnea in Adults With Traumatic Brain Injury: A Preliminary Investigation" (Archives of Physical Medicine and Rehabilitation, Vol. 82, Issue 3, pp. 316-321), J. Webster et al. investigated sleep-related breathing disorders in adults with traumatic brain injuries (TBI). The
L. Grossback et al. examined mandate perceptions and their causes in the paper "Comparing Competing Theories on the Causes of Mandate Perceptions" (American Journal of Political Science, Vol. 49, Issue 2, pp. 406-419). Following are data on the percentage of members in each chamber of Congress who
In Exercise 10.73, you conducted a nonpooled t-test to decide whether the mean number of acute postoperative days spent in the hospital is smaller with the dynamic system than with the static system.a. Using a pooled t-test, repeat that hypothesis test.b. Compare your results from the pooled and
In Example 10.6 on page 411, we conducted a nonpooled t-test, at the 5% significance level, to decide whether the mean operative time is less with the dynamic system than with the static system.a. Using a pooled t-test, repeat that hypothesis test.b. Compare your results from the pooled and
L. Petersen et al. evaluated the effects of integrated treatment for patients with a first episode of psychotic illness in the paper "A Randomised Multicentre Trial of Integrated Versus Standard Treatment for Patients With a First Episode of Psychotic Illness" (British Medical Journal, Vol. 331,
An independent golf equipment testing facility compared the difference in the performance of golf balls hit off a regular 2-3/4" wooden tee to those hit off a 3'' Stinger Competition golf tee. A Callaway Great Big Bertha driver with 10 degrees of loft was used for the test and a robot swung the
Anthropologists are still trying to unravel the mystery of the origins of the Etruscan empire, a highly advanced Italic civilization formed around the eighth century B.C. in central Italy. Were they native to the Italian peninsula or, as many aspects of their civilization suggest, did they migrate
Samples of adolescent offspring of diabetic mothers (ODM) and nondiabetic mothers (ONM) were taken by N. Cho et al. and evaluated for potential differences in vital measurements, including blood pressure and glucose tolerance. The study was published in the paper "Correlations Between the
Each pair of graphs in Fig. 10.8 shows the distributions of a variable on two populations. Suppose that, in each case, you want to perform a small-sample hypothesis test based on independent simple random samples to compare the means of the two populations. In each case, decide which, if any, of
Suppose that the sample sizes, n1 and n2, are equal for independent simple random samples from two populations.a. Show that the values of the pooled and nonpooled t-statistics will be identical. (Hint: Refer to Exercise 10.55 on page 408.)b. Explain why part (a) does not imply that the two t-tests
Tukey's Quick Test. In this exercise, we examine an alternative method, conceived by the late Professor John Tukey, for performing a two-tailed hypothesis test for two population means based on independent random samples. To apply this procedure, one of the samples must contain the largest
As we mentioned on page 403, the following relationship holds between hypothesis tests and confidence intervals: For a two-tailed hypothesis test at the significance level α, the null hypothesis H0: μ1 = μ2 will be rejected in favor of the alternative hypothesis Ha: μ1 ≠ μ2 if and only if
If the assumptions for a nonpooled t-interval are satisfied, the formula for a (1− α)-level upper confidence bound for the difference, μ1 − μ2, between two population means isFor a left-tailed hypothesis test at the significance level α, the null hypothesis H0: μ1 = μ2 will be rejected in
If the assumptions for a nonpooled t-interval are satisfied, the formula for a (1 ˆ’ Î±)-level lower confidence bound for the difference, Î¼1 ˆ’ Î¼2, between two population means isFor a right-tailed hypothesis test at the significance level Î±, the null hypothesis H0: Î¼1 = Î¼2
State the two conditions required for performing a paired t-procedure. How important are those conditions?
The A. C. Nielsen Company collects data on the TV viewing habits of Americans and publishes the information in Nielsen Report on Television. Suppose that you want to use a paired sample to decide whether the mean viewing time of married men is less than that of married women. a. Identify the
Refer to Problem 9, and find a 90% confidence interval for the difference in the mean lengths of time that ice stays on the two lakes. Interpret your result.
Paired; n = 75; Fig. 10.11Provides a type of sampling (independent or paired), sample size(s), and a figure showing the results of preliminary data analyses on the sample(s). For independent samples, the graphs are for the two samples; for a paired sample, the graphs are for the paired differences.
Independent; n1 = 25, n2 = 20; Fig. 10.12Provides a type of sampling (independent or paired), sample size(s), and a figure showing the results of preliminary data analyses on the sample(s). For independent samples, the graphs are for the two samples; for a paired sample, the graphs are for the
Independent; n1 = 17, n2 = 17; Fig. 10.13Provides a type of sampling (independent or paired), sample size(s), and a figure showing the results of preliminary data analyses on the sample(s). For independent samples, the graphs are for the two samples; for a paired sample, the graphs are for the
Independent; n1 = 40, n2 = 45; Fig. 10.14Provides a type of sampling (independent or paired), sample size(s), and a figure showing the results of preliminary data analyses on the sample(s). For independent samples, the graphs are for the two samples; for a paired sample, the graphs are for the
Independent; n1 = 20, n2 = 15; Fig. 10.15Provides a type of sampling (independent or paired), sample size(s), and a figure showing the results of preliminary data analyses on the sample(s). For independent samples, the graphs are for the two samples; for a paired sample, the graphs are for the
Paired; n = 18; Fig. 10.16Provides a type of sampling (independent or paired), sample size(s), and a figure showing the results of preliminary data analyses on the sample(s). For independent samples, the graphs are for the two samples; for a paired sample, the graphs are for the paired differences.
In the paper, "Drink and Be Merry? Gender, Life Satisfaction, and Alcohol Consumption Among College Students" (Psychology of Addictive Behaviors, Vol. 19, Issue 2, pp. 184-191), J. Murphy et al. examined the impact of alcohol use and alcohol-related problems on several domains of life satisfaction
I. Ertugrul et al. conducted a study to determine the association between insulin growth factor 1 (IGF-1) and bone mineral density (BMD) in men over 65 years of age. The researchers published their results in the paper "Relationship Between Insulin-Like Growth Factor 1 and Bone Mineral Density in
The Bureau of Labor Statistics publishes data on weekly earnings of full-time wage and salary workers in Employment and Earnings. Male and female workers were paired according to occupation and experience. Their weekly earnings, in dollars, are provided on the WeissStats CD. Use the technology of
Discuss the basic strategy for comparing the means of two populations based on a simple random paired sample.
On page 390, we presented data obtained by researchers studying the effect of hormone replacement therapy (HRT) on cholesterol levels. The researchers randomly divided 59 elderly women (75 years old or older) into a group of 39 women who were given HRT and a group of 20 women who were given
Recall from Chapter 1 (refer to page 30) that the Focus database and Focus sample contain information on the undergraduate students at the University of Wisconsin - Eau Claire (UWEC). Now would be a good time for you to review the discussion about these data sets. Open the Focus sample worksheet
Regarding the pooled and nonpooled t-procedures,a. What is the difference in assumptions between the two procedures?b. How important is the assumption of independent simple random samples for these procedures?c. How important is the normality assumption for these procedures?d. Suppose that the
In the paper, "Sex Differences in Static Strength and Fatigability in Three Different Muscle Groups" (Research Quarterly for Exercise and Sport, Vol. 61(3), pp. 238-242), J. Misner et al. published results of a study on grip and leg strength of males and females. The following data, in newtons, is
Refer to Problem 5. Determine a 90% confidence interval for the difference between the mean right-leg strengths of males and females. Interpret your result.
In the article "The Eastern Cottonmouth (Agkistrodon piscivorus) at the Northern Edge of Its Range" (Journal of Herpetology, Vol. 29, No. 3, pp. 391-398), C. Blem and L. Blem examined the reproductive characteristics of the eastern cottonmouth. The data in the following table, based on the results
Refer to Problem 7. Find a 98% confidence interval for the difference between the mean litter sizes of cottonmouths in Florida and Virginia. Interpret your result.
In the on-line paper "Changes in Lake Ice: Ecosystem Response to Global Change" (Teaching Issues and Experiments in Ecology, tiee.ecoed.net, Vol. 3), R. Bohanan et al. questioned whether there is evidence for global warming in long-term data on changes in dates of ice cover in three Wisconsin
Prerequisite to this exercise are Exercises 11.5. What do your graphs in parts (c) of those exercises illustrate about the impact of increasing sample size on sampling error? Explain your answer.
An issue of Science News (Vol. 163, No. 22, pp. 341–342) reported that the Women’s Health Initiative cast doubts on the benefit of hormonereplacement therapy. Researchers randomly divided 4532 healthy women over the age of 65 years into two groups. One group, consisting of 2229 women, received
The Organization for Economic Cooperation and Development (OECD) summarizes data on labor-force participation rates in OECD in Figures. Independent simple random samples were taken of 300 U.S. women and 250 Canadian women. Of the U.S. women, 215 were found to be in the labor force; of the Canadian
Neutropenia is an abnormally low number of neutrophils (a type of white blood cell) in the blood. Chemotherapy often reduces the number of neutrophils to a level that makes patients susceptible to fever and infections. G. Bucaneve et al. published a study of such cancer patients in the paper
In this exercise, apply Formulas 11.3 and 11.4 on pages 466 and 467 to the study on ordering vegetarian considered in Examples 11.8–11.10. a. Obtain the margin of error for the estimate of the difference between the proportions of men and women who sometimes order veg by taking half the length of
x1 = 10, n1 = 20, x2 = 18, n2 = 30; 80% confidence intervala. Use the two-proportions plus-four z-interval procedure as discussed on page 467 to find the required confidence interval for the difference between the two population proportions. b. Compare your result with the corresponding confidence
x1 = 18, n1 = 40, x2 = 30, n2 = 40; 80% confidence intervala. Use the two-proportions plus-four z-interval procedure as discussed on page 467 to find the required confidence interval for the difference between the two population proportions. b. Compare your result with the corresponding confidence
x1 = 14, n1 = 20, x2 = 8, n2 = 20; 90% confidence intervala. Use the two-proportions plus-four z-interval procedure as discussed on page 467 to find the required confidence interval for the difference between the two population proportions. b. Compare your result with the corresponding confidence
x1 = 15, n1 = 20, x2 = 18, n2 = 30; 90% confidence intervala. Use the two-proportions plus-four z-interval procedure as discussed on page 467 to find the required confidence interval for the difference between the two population proportions. b. Compare your result with the corresponding confidence
x1 = 18, n1 = 30, x2 = 10, n2 = 20; 95% confidence intervala. Use the two-proportions plus-four z-interval procedure as discussed on page 467 to find the required confidence interval for the difference between the two population proportions. b. Compare your result with the corresponding confidence
x1 = 30, n1 = 80, x2 = 15, n2 = 20; 95% confidence intervala. Use the two-proportions plus-four z-interval procedure as discussed on page 467 to find the required confidence interval for the difference between the two population proportions. b. Compare your result with the corresponding confidence
From Wikipedia’s on-line document “List of First Overall NBA Draft Picks,” we found that, since 1947, 11.3% of the number-one draft picks in the National Basketball Association have been other than U.S. nationals. a. Identify the population. b. Identify the specified attribute. c. Is the
Two USA TODAY/Gallup polls of 979 U.S. adults each, one in November 2001 and the other in March 2009, asked “Did the United States make a mistake in sending military forces to Afghanistan?” The numbers of affirmative responses in the two polls were 90 and 418, respectively. Determine a 95%
The Organization for Economic Cooperation and Development (OECD) conducts studies on unemployment rates by country and publishes its findings in the document Main Economic Indicators. Independent random samples of 100 and 75 people in the civilian labor forces of Finland and Denmark, respectively,
The Quinnipiac University Poll conducts nationwide surveys as a public service and for research. In one poll, participants were asked whether they thought eliminating the federal gas tax for the summer months is a good idea. The following problems are based on the results of that poll. a. Of 611
A Wall Street Journal article, titled “Hypertension Drug Linked to Cancer,” reported on a study of several types of high-blood-pressure drugs and links to cancer. For one type, called calcium-channel blockers, 27 of 202 elderly patients taking the drug developed cancer. For another type, called
According to an article in Time magazine, women are staying single longer these days, by choice. In 1963, 83% of women in the United States between the ages of 25 and 54 years were married, compared to 67% in 200 7. For 2007, a. Identify the population. b. Identify the specified attribute. c. Under
A Harris Poll asked Americans whether states should be allowed to conduct random drug tests on elected officials. Of 21,355 respondents, 79% said “yes.” a. Determine the margin of error for a 99% confidence interval. b. Without doing any calculations, indicate whether the margin of error is
According to an article in Science News, binge eating has been associated with a mutation of the gene for a brain protein called melanocortin 4 receptor (MC4R). In one study, F. Horber of the Hirslanden Clinic in Zurich and his colleagues genetically analyzed the blood of 469 obese people and found
In each of parts (a)–(c), we have given a likely range for the observed value of a sample proportion pˆ. Based on the given range, identify the educated guess that should be used for the observed value of pˆ to calculate the required sample size for a prescribed confidence level and margin of
In each of parts (a)–(c), we have given a likely range for the observed value of a sample proportion pˆ. Based on the given range, identify the educated guess that should be used for the observed value of pˆ to calculate the required sample size for a prescribed confidence level and margin of
x = 8, n = 40, 95% level. we have given the number of successes and the sample size for a simple random sample from a population. In each case, do the following tasks. a. Determine the sample proportion. b. Decide whether using the one-proportion z-interval procedure is appropriate. c. If
x = 10, n = 40, 90% level. We have given the number of successes and the sample size for a simple random sample from a population. In each case, do the following tasks. a. Determine the sample proportion. b. Decide whether using the one-proportion z-interval procedure is appropriate. c. If
x = 35, n = 50, 99% level. We have given the number of successes and the sample size for a simple random sample from a population. In each case, do the following tasks. a. Determine the sample proportion. b. Decide whether using the one-proportion z-interval procedure is appropriate. c. If
x = 40, n = 50, 95% level. We have given the number of successes and the sample size for a simple random sample from a population. In each case, do the following tasks. a. Determine the sample proportion. b. Decide whether using the one-proportion z-interval procedure is appropriate. c. If
x = 16, n = 20, 90% level. We have given the number of successes and the sample size for a simple random sample from a population. In each case, do the following tasks. a. Determine the sample proportion. b. Decide whether using the one-proportion z-interval procedure is appropriate. c. If
x = 3, n = 100, 99% level. We have given the number of successes and the sample size for a simple random sample from a population. In each case, do the following tasks. a. Determine the sample proportion. b. Decide whether using the one-proportion z-interval procedure is appropriate. c. If
An issue of Time Style and Design reported on a poll conducted by Schulman Ronca & Bucuvalas Public Affairs about the shopping habits of wealthy Americans. A total of 603 interviews were conducted among a national sample of adults with household incomes of at least $150,000. Of the adults
In 2005, the Terri Schiavo case focused national attention on the issue of withdrawal of life support from terminally ill patients or those in a vegetative state. A Harris Poll of 1010 U.S. adults was conducted by telephone on April 5–10, 2005. Of those surveyed, 140 had experienced the death of
In the article “Explaining an Unusual Allergy,” appearing on the Everyday Health Network, Dr. A. Feldweg explained that allergy to sulfites is usually seen in patients with asthma. The typical reaction is a sudden increase in asthma symptoms after eating a food containing sulfites. Studies are
A Reader’s Digest/Gallup Survey on the drinking habits of Americans estimated the percentage of adults across the country who drink beer, wine, or hard liquor at least occasionally. Of the 1516 adults interviewed, 985 said that they drank. a. Determine a 95% confidence interval for the
The U.S. Environmental Protection Agency recently reported that confined animal feeding operations (CAFOs) dump 2 trillion pounds of waste into the environment annually, contaminating the ground water in 17 states and polluting more than 35,000 miles of our nation’s rivers. In a survey of 1000
From fall 1998 through mid 1999, Malaysia was the site of an encephalitis outbreak caused by the Nipah virus, a paramyxovirus that appears to spread from pigs to workers on pig farms. As reported by K. Goh et al. in the paper “Clinical Features of Nipah Virus Encephalitis among Pig Farmers in
Suppose that you have been hired to estimate the percentage of adults in your state who are literate. You take a random sample of 100 adults and find that 96 are literate. You then obtain a 95% confidence interval of 0.96 ± 1.96 · √(0.96)(0.04)/100, or 0.922 to 0.99 8. From it you conclude that
The infant mortality rate (IMR) is the number of infant deaths per 1000 live births. Suppose that you have been commissioned to estimate the IMR in Singapore. From a random sample of 1109 live births in Singapore, you find that 0.361% of them resulted in infant deaths. You next find a 90%
An ABCNEWS Poll found that Americans now have relatively warm feelings toward Russia, a former adversary. The poll, conducted by telephone among a random sample of 1043 adults, found that 647 of those sampled consider the two countries friends. The margin of error for the poll was plus or minus 2.9
According to the Internal Revenue Service, among people entitled to tax refunds, those who file online receive their refunds twice as fast as paper filers. A study conducted by International Communications Research (ICR) of Media, Pennsylvania, found that 57% of those polled said that they are not
Refer to Exercise 11.25. a. Determine the margin of error for the estimate of p. b. Obtain a sample size that will ensure a margin of error of at most 0.01 for a 95% confidence interval without making a guess for the observed value of pˆ. c. Find a 95% confidence interval for p if, for a sample of
Refer to Exercise 11.26. a. Find the margin of error for the estimate of p. b. Obtain a sample size that will ensure a margin of error of at most 0.02 for a 95% confidence interval without making a guess for the observed value of pˆ. c. Find a 95% confidence interval for p if, for a sample of the
Refer to Exercise 11.27. a. Determine the margin of error for the estimate of the percentage. b. Obtain a sample size that will ensure a margin of error of at most 1.5 percentage points for a 99% confidence interval without making a guess for the observed value of pˆ. c. Find a 99% confidence
Refer to Exercise 11.28. a. Find the margin of error for the estimate of the percentage. b. Obtain a sample size that will ensure a margin of error of at most 5 percentage points for a 90% confidence interval without making a guess for the observed value of pˆ. c. Find a 90% confidence interval
A company manufactures goods that are sold exclusively by mail order. The director of market research needed to test market a new product. She planned to send brochures to a random sample of households and use the proportion of orders obtained as an estimate of the true proportion, known as the
On Thursday, June 13, 1996, then Arizona Governor Fife Symington was indicted on 23 counts of fraud and extortion. Just hours after the federal prosecutors announced the indictment, several polls were conducted of Arizonans asking whether they thought Symington should resign. A poll conducted by
The headline read “President’s Job Ratings Fall to Lowest Point of His Presidency.” A Harris Poll taken April 5–10, 2005, of 1010 U.S. adults found that 444 of them approved of the way that President George W. Bush was doing his job. Find and interpret a 95% confidence interval for the
Answer the following questions about the basic notation and terminology for proportions. a. What is a population proportion? b. What symbol is used for a population proportion? c. What is a sample proportion? d. What symbol is used for a sample proportion? e. For what is the phrase “number of
A major hurricane is a category 3, 4, or 5 hurricane on the Saffir/Simpson Hurricane Scale. From the document “The Deadliest, Costliest, and Most Intense United States Tropical Cyclones From 1851 to 2004” (NOAA Technical Memorandum, NWS TPC-4, Updated 2005) by E. Blake et al., we found that of
In a nationwide survey of U.S. adults by the Cincinnati-based research firm Directions Research Inc., only 276 of the 1063 respondents said they would purchase or lease a new car from a manufacturer that had declared bankruptcy. Determine and interpret a 90% confidence interval for the percentage
In the article “Bottled Natural Mineral Waters in Romania” (Environmental Geology Journal, Vol. 46, Issue 5, pp. 670–674), A. Feru compared the mineral, ionic, and carbon dioxide content of mineral-water source locations in Romania. Of 31 randomly selected source locations, 22 had natural
In discussing the sample size required for obtaining a confidence interval with a prescribed confidence level and margin of error, we made the following statement: “If we have in mind a likely range for the observed value of pˆ, then, in light of Fig. 11.1, we should take as our educated guess

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