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Introductory Statistics Exploring The World Through Data 2nd Edition Robert Gould, Colleen Ryan - Solutions

Triglycerides are a form of fat found in the body. Using data from NHANES, we looked at whether men have higher triglyceride levels than women.a. Report the sample means, and state which group had the higher sample mean triglyceride level. Refer to the Minitab output in figure (A).b. Carry out a
Calls Answers.com claims that the mean length of all cell phone conversations in the United States is 3.25 minutes (3 minutes and 15 seconds). Assume that this is correct, and also assume that the standard deviation is 4.2 minutes. a. Describe the shape of the distribution of the length of cell
When you have your blood pressure taken, the larger number is the systolic blood pressure. Using data from NHANES, we looked at whether men and women have different systolic blood pressure levels.a. Report the two sample means, and state which group had the higher sample mean systolic blood
Report and interpret the 95% confidence interval for the difference in mean triglyceride level for men and women (refer to the Minitab output in Exercise 9.59). Does this support the hypothesis that men and women differ in mean triglyceride level? Explain.
A random sample of 14 college women and a random sample of 19 college men were separately asked to estimate how much they spent on clothing in the last month. The table shows the data. Test the hypothesis that the population mean amounts spent on clothes are different for men and women. Use a
A random sample of male college baseball players and a random sample of male college soccer players were obtained independently and weighed. The table shows the unstacked weights (in pounds). The distributions of both data sets suggest that the population distributions are roughly Normal. Determine
In Exercise 9.63 you could not reject the null hypothesis that the mean amount spent by men and the mean amount spent by women for clothing are the same, using a two-tailed test with a significance level of 0.05. a. If you found a 95% confidence interval for the difference between means, would it
In Exercise 9.64, you could reject the null hypothesis that the mean weights of soccer and baseball players were equal using a two-tailed test with a significance level of 0.05. a. If you found a 95% confidence interval for the difference between means, would it capture 0? Explain. b. If you found
The prices of a sample of books at University of California at Santa Barbara (UCSB) were obtained by statistics students Ricky Hernandez and Elizabeth Alamillo. Then the cost of books for the same subjects (at the same level) were obtained for California State University at Northridge (CSUN).
The prices of a random sample of comparable (matched) textbooks from two schools were recorded. We are comparing the prices at OC (Oxnard Community College) and CSUN (California State University at Northridge). Assume that the population distribution of differences is approximately Normal. Each
In a statistics class taught by one of the authors, students took their pulses before and after being frightened. The frightening event was having the teacher scream and run from one side of the room to the other. The pulse rates (beats per minute) of the women before and after the scream were
Follow the instructions for Exercise 9.69, but use the data for the men in the class. Test the hypothesis that the mean of college men's pulse rates is higher after a fright, using a significance level of 0.05.
A student compared organic food prices at Target and Whole Foods. The same items were priced at each store. The first three items are shown in Figure A. Choose the correct output (B or C) for the appropriate test, explaining why you chose that output. Then test the hypothesis that the population
The birth weights of 35 babies whose mothers did not smoke and 22 babies whose mothers smoked were compared; weights were in grams. (Source: Smoking Mothers, Holcomb 2006, accessed via StatCrunch. Owner: kupresanin99) Test the hypothesis that the population mean birth weight is larger for mothers
Data for the ages of grooms and their brides for a random sample of 31 couples in Ventura County, California, were obtained and can be found at this text's website.a. Compare the sample means.b. Test the hypothesis that there is a significant difference in mean ages of brides and grooms, using a
Surfers and statistics students Rex Robinson and Sandy Hudson collected data on the number of days on which surfers surfed in the last month for 30 longboard (L) users and 30 shortboard (S) users. Treat these data as though they were from two independent random samples. Test the hypothesis that the
A random sample of students at Oxnard College reported what they believed to be their heights in inches. Then the students measured each others' heights in centimeters, without shoes. The data shown are for the men. Assume that the conditions for t-tests hold.a. Convert heights in inches to
Jacqueline Loya, a statistics student, asked students with jobs how many times they went out to eat in the last week. There were 25 students who had part-time jobs and 25 students who had full-time jobs. Carry out a hypothesis test to deter mine whether the mean number of meals out per week for
Compare the weights of backpacks of men and women. (Source: StatCrunch: Backpack. Owner: Wikipeterson)
Amber Sanchez, a statistics student, collected data on the prices of the same items at the Navy commissary on the naval base in Ventura County, California, and a nearby Kmart. The items were matched for content, manufacturer, and size and were priced separately.a. Report and compare the sample
Compare the weekday and weekend/holiday hours of sleep. Each pair of numbers is from one randomly selected person. This is a different set of data from the one in the chapter. (Source: StatCrunch Survey: Responses to Sleep survey. Owner: scsurvey)
Compare the numbers of pairs of shoes for men and women. (Source: StatCrunch Survey: Responses to Shoe survey. Owner: scsurvey)
A McDonald's fact sheet says their cones should weigh 3.18 ounces (converted from grams). Suppose you take a random sample of four cones, and the weights are 4.2, 3.4, 3.9, and 4.4 ounces. Assume that the population distribution is Normal, and, for all three parts, report the alternative
A random sample of 10,000 UTA colas was taken to see whether the mean weight was 16 fluid ounces, as marked on the container. The null hypothesis is that the population mean is 16 ounces. For all three parts, report the alternative hypothesis, the t-value, the p-value, and your conclusion. Refer to
Brain size for 20 random women and 20 random men was obtained and is reported in the table (in hundreds of thousands of pixels shown in an MRI). Test the hypothesis that men tend to have larger brains than women at the 0.05 level.
Users of StatCrunch were polled and asked to indicate their level of happiness from 1 to 100 (most happy). The output shows the results of a t-test. There were 297 females and 380 males polled. Assume the sample is random.a. Which had a higher sample mean, and how do you know?b. Test the hypothesis
Elena Lucin, a statistics student, collected the data in the table showing heart rate (beats per minute) for a random sample of coffee drinkers before and 15 minutes after they drank coffee. Carry out a complete analysis, using the techniques you learned in this chapter. Use a 5% significance level
The final exam grades for a sample of day time statistics students and evening statistics students at one college are reported. The classes had the same instructor, covered the same material, and had similar exams. Using graphical and numerical summaries, write a brief description about how grades
The number of hours per week of television viewing for random samples of fifth grade boys and fifth grade girls were obtained. Each student logged his or her hours for one Monday-through-Friday period. Assume that the students were independent; for example there were no pairs of siblings who
The average income in the District of Columbia in 2013 was $76,000 per person per year, and that was larger than the average for any state. Suppose the standard deviation is $35,000 and the distribution is right-skewed. Suppose we take a random sample of 100 residents of D.C. a. What value should
Reaction distances in centimeters for a random sample of 40 college students were obtained. Shorter distances indicate quicker reactions. Each student tried the experiment both with his or her dominant hand, and with his or her nondominant hand, catching the meter stick. The subjects all started
A survey was done comparing the number of hours of sleep for workers on the day shift and for workers on the night shift. Assume the sample is random. Descriptive statistics are shown. The output of a t-test is also shown.a. Compare the sample means descriptively in at least one sentence.b. Test
Grocery prices of the same items were compared at Target and Whole Foods. Assume the sampling was random. The descriptive statistics are shown, and the results of a t-test are shown.a. Compare the sample means descriptively.b. Perform a hypothesis test to determine whether the means are
A random sample of 10 Democrats and 10 Republicans were asked what is the largest value (in percentage) that one should be expected to pay as taxes.a. Test the hypothesis that Democrats have a higher mean than Republicans, using a 0.05 significance level. Assume the data sets are Normal.b. Create a
Do boys who feel that they are "underweight" actually weigh less than boys who feel that they are "about right" in weight? If not, this suggests that boys do not have a good sense of their weight relative to others. The table has a random sample of observations from the Youth At Risk survey, and
The table shows the prices of identical groceries at 7-Eleven and at Vons.a. Test the hypothesis that the mean price at 7-Eleven is more than the mean price at Vons, at the 0.05 level. Assume that the sampling is random and the samples are Normal.b. Although a two-sample t-test is not appropriate
The table shows the heights (in inches) of a random sample of students and their parent of the same gender. Test the hypothesis that the mean for the students is more than the mean for the parents, at the 0.05 level. Assume the data are Normal.a. Use the paired t-test that is appropriate.b. Use the
Why do we calculate s by dividing by n €“ 1, rather than just n?The reason is that if we divide by n - 1, then s2 is an unbiased estimator of Ïƒ2, the population variance. We want to show that s2 is an unbiased estimator of Ïƒ2, sigma squared. The mathematical proof that this is true is
Refer to Exercise 10.9. This data table compares women who viewed high levels of television violence as children with those who did not in order to study the differences with regard to physical abuse of their partners as adults. The women categorized as physically abusive had hit, grabbed, or
According to the website MedicalNewsToday.com, coronary artery disease accounts for about 40% of deaths in the United States. Many people believe this is due to modern-day factors such as high-calorie fast food and lack of exercise. However, a study published in the Journal of the American Medical
According to a Pew Poll done in 2010, 50% of adults aged 25-29 had access only to a cell phone (no landline). Assume that you randomly sample 50 adults aged 25-29, and ask whether they have access only to a cell phone. Suppose that 30 say yes and 20 say no. Calculate the observed value of the
Violins Stradivarius violins, made in the 1700s by a man of the same name, are worth millions of dollars. They are prized by music lovers for their uniquely rich, full sound. In September 2009, an audience of experts took part in a blind test of violins, one of which was a Stradivarius. There were
Coin Flips You flip a coin 100 times and get 58 heads and 42 tails. Calculate the chi-square statistic by hand showing your work, assuming the coin is fair.
Refer to Exercise 10.9. The data table compares men who viewed high levels of television violence as children with those who did not, in order to study the differences with regard to physical abuse of their partners as adults. Report the observed value of the chi-square statistic.
Refer to Exercise 10.10. The data table compares women who viewed high levels of television violence as children with those who did not, in order to study the differences with regard to physical abuse of their partners as adults. Calculate the observed value of the chi-square statistic.
One of the authors collected data from a class to see whether humans made selections randomly, as a random number generator would. Each of 38 students had to pick an integer from one to five. The data are summarized in the table.A true random number generator would create roughly equal numbers of
We counted ones, twos, threes, fours, and fives from a few lines of a random number table, and we should expect to get equal numbers of each. (We ignored the sixes, sevens, eights, nines, and zeros.) There were 14 ones, 12 twos, 16 threes, 11 fours, and 8 fives, which is 61 numbers in the
A penny was spun on a hard, flat surface 50 times, and the result was 15 heads and 35 tails. Using a chi-square test for goodness of fit, test the hypothesis that the coin is biased, using a 0.05 level of significance.
Time magazine (July 9, 2012) reported that 50% of children 3€“5 years old experience frequent nightmares. Suppose in a random sample of 200 children, 112 experienced frequent nightmares. Can you reject the hypothesis that 50% is the correct population percentage, using a significance
The table shows the results of rolling a six-sided die 120 times. Outcome on Die Frequency 1 .............. 27 2 .............. 20 3 .............. 22 4 .............. 23 5 .............. 19 6 .............. 9 Test the hypothesis that the die is not fair. A fair die should produce equal numbers
Repeat the chi-square test (all four steps) from Exercise 10.23, but this time assume that you got exactly 20 outcomes in each of the six categories. Refer to the figure. Explain.
Violins Professional musicians listened to five violins being played, without seeing the instruments. One violin was a Stradivarius, and the other four were modern-day violins. When asked to pick the Stradivarius (after listening to all five), 39 got it right and 113 got it wrong. a. Use the
Exercise 10.11 on artery disease in mummies indicated that 9 out of 16 mummies showed heart disease (hardening of the arteries). Test the hypothesis that the population proportion of mummies with hardening of the arteries is not the same as in the modern United States (that it is not 40%). Use a
A statistics student conducted a study in Ventura County, California, that looked at criminals on probation who were under 15 years of age to see whether there was an association between the type of crime (violent or nonviolent) and gender. Violent crimes involve physical contact such as hitting or
Origin The table shows the country of origin and the percentage of foreign-born people in the United States in 2000 and 2010 for the four countries of origin with the highest percentages (2012 World Almanac and Book of Facts). Give two reasons why you should not do a chi-square test with these data.
A study reported in the medical journal Obesity in 2009 analyzed data from the National Longitudinal Study of Adolescent Health. Obesity was defined as having a body mass index (BMI) of 30 or more. The research subjects were followed from adolescence to adult hood, and all the people in the sample
Loss Overweight or obese adults from psychiatric programs were recruited and randomly assigned to a treatment group or control group. Patients in the treatment group received both weight-management sessions plus exercise sessions plus their usual care. Patients in the control group received their
The data table compares men who viewed television violence with those who did not, in order to study the differences in physical abuse of the spouse. For the men in the table, test whether television violence and abusiveness are associated, using a significance level of 0.05.Refer to the Minitab
The data table compares women who viewed television violence with those who did not, in order to study the differences in physical abuse of the spouse (Husemann et al. 2003). Test whether television violence and abusiveness are associated, using a significance level of 0.05.Refer to the Minitab
The table shows the results of a two-way table of gender and whether a person is happy in his or her marriage, according to data obtained from a General Social Survey.Happiness of Marriage X Respondent's Sex Cross Tabulation Counta. If we carry out a test to determine whether these variables are
Randomly chosen people were observed for about 10 seconds in several public places, such as malls and restaurants, to see whether they smiled during that time. The table shows the results for different age groups.a. Find the percentage of each age group that were observed smiling, and compare these
The Perry Preschool Project was created in the early 1960s by David Weikart in Ypsilanti, Michigan. One hundred and twenty three African American children were randomly assigned to one of two groups: One group enrolled in the Perry Preschool, and one did not enroll. Follow-up studies were done for
The Perry Preschool Project data presented in Exercise 10.39 (Schweinhart et al. 2005) can be divided to see whether the preschool attendance effect is different for males and females. The table shows a summary of the data for females, and the figure shows Minitab output that you may use.a. Find
The Perry Preschool Project data presented in Exercise 10.39 can be divided to see whether there are different effects for males and females. The table shows a summary of the data for males (Schweinhart et al. 2005).a. Find the graduation rate for males who went to preschool, and com pare it with
A survey was taken of a random sample of people noting their gender and asking whether they agreed with the "Occupy Wall Street" (OWS) movement (Source: StatCrunch: Responses to Occupy Wall Street Survey. Owner: scsurvey). Minitab results are shown.a. Find the percentage of men and the percentage
Mingrone et al. reported the results of an experiment on severely obese patients who had diabetes for at least 5 years. Sixty patients were randomly divided into three groups. One group received medical therapy only (control group), a second group received gastric bypass surgery, and a third group
A study conducted in Uganda and Kenya looked at heterosexual couples in which one of the partners was HIV-positive and the other was not. The person in each couple who was not HIV-positive was randomly assigned to one of three study regimens: tenofovir (TDF), combination teno fovir-emtricitabine
A study was done to see whether participants would ignore a sign that said, "Elevator may stick between floors. Use the stairs." The people who used the stairs were said to be compliant, and those who used the elevator were noncompliant. The study was done in a university dormitory on the ground
Kang et al. reported on a randomized trial of early surgery for patients with infective endocarditis (a heart infection). Of the 37 patients assigned to early surgery, 1 had a bad result (died, had an embolism, or had a recurrence of the problem within 6 months). Of the 39 patients with
A study was done on female mice to see whether the amount of light affects the risk of develop ing tumors. Fifty mice were randomly assigned to a regimen of 12 hours of light and 12 hours of dark (LD). Fifty similar mice were assigned to 24 hours of light (LL). The study began when the mice were 2
Computed tomography (CT) scans are used to diagnose the need for the removal of the appendix. CT scans give the patient a large level of radiation, which has risks, especially for young people. There is a new form of CT scanning called low-dose CT, which was tested to see whether it was inferior
The data on hospitalizations for swine flu, obtained in May 2009 from the Centers for Disease Control, is summarized in the accompanying table. The table looks at the relation between Age Group and Hospitalization, for all swine flu victims in the United States (www.cdc.gov).Because some of the
A random sample of nurses working night shifts were asked whether they were fatigued (no or yes) and what form of sleep aid they used. Assume that each person used one sleep aid. The table shows the results.a. Why is a chi-square test for independence inappropriate for this data set?b. Combine some
The data in the table are from a General Social Survey and concern gender and political party.a. Find the expected counts and report the smallest. Could we use the table as is, without combining categories?b. Create a new table, using the data from the table shown, with fewer categories. Merge the
The data in the table come from a General Social Survey. The top row is the number of children reported for the respondents. The respondents also reported their level of happiness; Very H means Very Happy, and so on. The counts are shown in the table. Is happiness associated with having at least
A study was done on children, aged 6 months to 18 years, who had nonlethal scorpion stings. Each child was randomly assigned to receive an experimental antivenom or a placebo. "Good" results were no symptoms after four hours and no detectable plasma venom.The alternative hypothesis is that the
Rats had a choice of freeing another rat or eat ing chocolate by themselves. Most of the rats freed the other rat and then shared the chocolate with it. The table shows the data concerning the gender of the rat in control.a. Can a chi-square test for homogeneity or independence be performed with
A statistics student performed a study on male and female criminals 15 years old and under who were on probation in Ventura County, California. The purpose was to see whether there was an association between type of crime (violent or nonviolent) and gender. Violent crimes involve physical contact
In a randomized, placebo controlled, double-blind study, 55 children (5 to 11 years old) who had an egg allergy were randomly assigned either oral immunotherapy or placebo. After 10 months of therapy, 22 of the 40 given the therapy passed the food challenge (did not react badly to eggs), and none
The Perry Preschool Project discussed in Exercises 10.39-10.41 found that 8 of the 58 students who attended preschool had at least one felony arrest by age 40 and that 31 of the 65 students who did not attend preschool had at least one felony arrest (Schweinhart et al. 2005).a. Compare the
In Montreal, Canada, an experiment was done with parents of children who were thought to have a high risk of committing crimes when they became teenagers. Some of the families were randomly assigned to receive parental training, and the others were not. Out of 43 children whose parents were
A nationwide representative sample of students in grades 7-12 that was done in May and June of 2011 studied the sexual harassment of students. 56% of the girls experienced sexual harassment, and 40% of the boys experienced it. Assume this was a single random sample. Sexual harassment was determined
In Ventura County in 2013, it was thought that 40% of men 50 years old or older had never been screened for prostate cancer. Suppose a random sample of 80 of these men shows that 30 of them had never been screened. a. What is the observed frequency of men who said they had not been screened? b.
Campbell et al. reported the results of an experiment with children. Some were randomly assigned to a new "intensive" preschool and others to the regular preschool. Then it was noted whether each child had a felony conviction by age 21.a. Test the hypothesis that type of preschool and a later
Cockroaches tend to rest in groups and prefer dark areas. In a study published in Science Magazine in November 2007, cockroaches were introduced to a brightly lit, enclosed area with two different available shelters, one darker than the other. Each time a group of cockroaches was put into the
Refer to the description in Exercise 10.71. There were 22 trials with only cockroaches (no robots) that went under one shelter. In 16 of these 22 trials, the group chose the darker shelter, and in 6 of the 22 the group chose the lighter shelter.There were 28 trials with a mixture of real
In July 2013, Jeff Witmer obtained a data set from the Tampa Bay Times after the Zimmerman case was decided. Zimmerman shot and killed Trayvon Martin (an unarmed black teenager) and was acquitted. The data set concerns "stand your ground" cases with male defendants. Some of these were fatal
Here are the conviction rates with the "stand your ground" data mentioned in the previous exercise. "White shooter on non-white" means that a white assailant shot a minority victim.a. Which has the higher conviction rate: white shooter on non-white or non-white shooter on white? b. Create a two-way
In Ventura County in 2013, it was thought that 16% of women over 40 had not had a mammogram in the last two years. Suppose a random sample of 140 of these women shows that 28 of them said they had not had a mammogram in the last two years. a. What is the observed frequency of women who said they
A study done by Husemann et al. and published in Developmental Psychology in 2003 compared men who viewed high levels of television violence as children with those who did not in order to study the differences with regard to physical abuse of their partners as adults. The men categorized as
Assume you have four groups to compare through hypothesis tests and confidence intervals, and you want the overall level of significance to be 0.05. a. How many possible comparisons are there? b. What is the Bonferroni-corrected value of the significance level for each comparison? c. What is the
Use the data from Exercise 11.7 and find Bonferroni-corrected intervals for all three comparisons assuming an overall confidence level of 95%, that is, an individual confidence level of 98.33%. Then state whether the means are significantly different based on whether the intervals capture 0 or not.
Use the data from Exercise 11.8 and find Bonferroni-corrected intervals for all three comparisons assuming an overall confidence level of 95%, using an individual confidence level of 98.33%. Then state whether the means are significantly different based on whether the intervals capture 0 or not.
The table shows the number of work hours €œlast week€ from a random sample of people during the €œGreat Recession,€ as reported by the 2008 General Social Survey. Unemployed people were not included. The headings show educational level: LTHS stands for €œless than high school,€
Use the data in the previous question. Find six confidence intervals (at individual level of 99.17%), and use them to determine which of the education levels have means that are significantly different from which others at an overall 5% level of confidenceThe table shows the number of work hours
Refer to the figure. Assume that all distributions are symmetric (therefore the sample mean and median are approximately equal) and that all the samples are the same size. Imagine carrying out two ANOVAs. The first compares the means based on samples A, B, and C (above the horizontal line), and the
Refer to the figure. Assume that all data sets are symmetric and that all the samples are the same size. Imagine carrying out two ANOVAs. The first compares the means based on samples A, B, and C (above the horizontal line), and the other is based on samples G, H, and K (below the horizontal line).
Refer to the StatCrunch output from National Health and Nutrition Examination Survey (NHANES) data, which shows the association between marital status and cholesterol. Assume the population distributions are close enough to Normal to justify using ANOVA.a. Write the null and alternative hypotheses
Test the hypothesis that people with different marital statuses differ in mean systolic blood pressure, using a significance level of 0.05. Refer to the StatCrunch output from NHANES data.a. Write the null and alternative hypotheses for the association between marital status and blood pressure.b.
A random survey was done at a small Lutheran college, and the students were asked how many hours a week they spent studying outside of class time. They were also asked what class they were in (1 = Freshman, 2 = Sophomore, 3 = Junior, and 4 = Senior).a. Figure out the missing SS (sum of squares).b.

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