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Homework answers / question archive / Think and Answer requires you to answer two questions
Think and Answer requires you to answer two questions. For each question, do not simply provide an answer; make sure you explain how you arrived at that answer. Even if your reasoning is wrong, you will still be credited for participation.
Each weekly Think and Answer post(s) is worth 2% of your final grade.
Week 1 Think and Answer
What is Wrong with These Statements?
1. The air temperature was 33° F in the night and 66° F in the day. So in the day it was twice as warm as in the night.
2. The United Nations Organization declared that the world’s sixbillionth inhabitant was born on October 12, 1999 in Bosnia.
True or False?
3. When we are selecting the class width, we may, for more convenience, round it off to the nearest whole number.
4. If you add 1 to each score in a data set, the mean for this set will also increase by 1.
HomeWork Week 1
Ch.1
Sec 11:
Sampling Method. In Exercises 9–12, determine whether the sampling method appears to be sound or is flawed.
What’s Wrong? In Exercises 25–28, identify what is wrong.
Percentages. In Exercises 29–36, answer the given questions, which are related to percentages.
30. Checking Job Applicants In a study conducted by the Society for Human Resource Management, 347 human resource professionals were surveyed. Of those surveyed, 73% said that their companies conduct criminal background checks on all job applicants.
Sec 12: ##
In Exercises 5–12, identify whether the given value is a statistic or a parameter.
In Exercises 13–20, determine whether the data are from a discrete or continuous data set.
20. Texting Fatalities The Insurance Institute for Highway Safety collects data consisting of the numbers of motor vehicle fatalities caused by driving while texting.
In Exercises 21–28, determine which of the four levels of measurement (nominal, ordinal, interval, ratio) is most appropriate.
26.Movie Ratings The author rated the movie Star Wars: The Force Awakens with 5 stars on a scale of 5 stars.
28.Body Temperatures Body temperatures (in degrees Fahrenheit) listed in Data Set 3 “Body Temperatures”
Temperature Day 1 
Temperature Day 2 

Subject 
Age 
Sex 
Smoke 
8 AM 
12 AM 
8 AM 
12 AM 
1 
22 
M 
Y 
98.0 
98.0 
98.0 
98.6 
2 
23 
M 
Y 
97.0 
97.6 
97.4 

3 
22 
M 
Y 
98.6 
98.8 
97.8 
98.6 
Body Temperatures (in degrees Fahrenheit) of Healthy Adults 
In Exercises 29–32, identify the level of measurement of the data as nominal, ordinal, interval, or ratio. Also, explain what is wrong with the given calculation.
30.Social Security Numbers As part of a project in a statistics class, students report the last four digits of their Social Security numbers, and the average (mean) of those digits is computed to be 4.7.
32.College Ranks As of this writing, U.S. News & World Reportranked national universities, including these results: Princeton (1), Harvard (2), Yale (3), and Columbia (4). The difference between Princeton and Harvard is the same as the difference between Yale and Columbia.
Sec 13:
Exercises 5–8 refer to the study of an association between which ear is used for cell phone calls and whether the subject is lefthanded or righthanded. The study is reported in “Hemispheric Dominance and Cell Phone Use,” by Seidman et al., JAMA Otolaryngology— Head & Neck Surgery, Vol. 139, No. 5. The study began with a survey emailed to 5000 people belonging to an otology online group, and 717 surveys were returned. (Otology relates to the ear and hearing.)
6.Experiment or Observational Study Is the study an experiment or an observational study? Explain.
8.Sampling Method Assume that the population consists of all students currently in your statistics class. Describe how to obtain a sample of six students so that the result is a sample of the given type.
In Exercises 9–20, identify which of these types of sampling is used: random, systematic, convenience, stratified, or cluster.
10.Sexuality of Women The sexuality of women was discussed in Shere Hite’s book Women and Love: A Cultural Revolution. Her conclusions were based on sample data that consisted of 4500 mailed responses from 100,000 questionnaires that were sent to women.
13.Driving A student of the author conducted a survey on driving habits by randomly selecting three different classes and surveying all of the students as they left those classes.
15.Dictionary The author collected sample data by randomly selecting five books from each of the categories of science, fiction, and history. The numbers of pages in the books were then identified.
18.Exit Polls During the last presidential election, CNN conducted an exit poll in which specific polling stations were randomly selected and all voters were surveyed as they left the premises.
Critical Thinking: What’s Wrong? In Exercises 21–28, determine whether the study is an experiment or an observational study, and then identify a major problem with the study.
Ch.2
Sec 21:
Time (sec) 
Frequency 
?60–119 
?7 
120–179 
22 
180–239 
14 
240–299 
?2 
300–359 
?5 
table for Exercise 1 mcdonald’s dinner service times 
In Exercises 5–8, identify the class width, class midpoints, and class boundaries for the given frequency distribution. Also identify the number of individuals included in the summary. The frequency distributions are based on real data from Appendix B.
Age (yr) of Best Actress When Oscar Was Won 
Frequency 
20–29 
29 
30–39 
34 
40–49 
14 
50–59 
?3 
60–69 
?5 
70–79 
?1 
80–89 
?1 
Constructing Frequency Distributions. In Exercises 11–18, use the indicated data to construct the frequency distribution. (The data for Exercises 13–16 can be downloaded at TriolaStats.com.)
125 
203 
205 
221 
225 
229 
233 
233 
235 
236 
236 
237 
238 
238 
239 
240 
240 
240 
240 
241 
241 
242 
242 
242 
243 
243 
244 
245 
245 
245 
245 
246 
246 
248 
248 
248 
249 
249 
250 
251 
252 
253 
253 
255 
255 
256 
257 
258 
262 
264 
17Analysis of Last Digits Heights of statistics students were obtained by the author as part of an experiment conducted for class. The last digits of those heights are listed below. Construct a frequency distribution with 10 classes. Based on the distribution, do the heights appear to be reported or actually measured? What do you know about the accuracy of the results?
0000000001123334555555555555555668889
Cumulative Frequency Distributions. In Exercises 21 and 22, construct the cumulative frequency distribution that corresponds to the frequency distribution in the exercise indicated.
Age (yr) of Best Actress When Oscar Was Won 
Frequency 
20–29 
29 
30–39 
34 
40–49 
14 
50–59 
?3 
60–69 
?5 
70–79 
?1 
80–89 
?1 
Sec 22:
Interpreting a Histogram. In Exercises 5–8, answer the questions by referring to the following Minitabgenerated histogram, which depicts the weights (grams) of all quarters listed in Data Set 29 “Coin Weights” in Appendix B. (Grams are actually units of mass and the values shown on the horizontal scale are rounded.)
Constructing Histograms. In Exercises 9–16, construct the histograms and answer the given questions.
Sec 23:
Stemplots. In Exercises 7 and 8, construct the stemplot.
TimeSeries Graphs. In Exercises 9 and 10, construct the timeseries graph.
71.6 
69.9 
70.8 
71.5 
72.0 
71.4 
73.8 
74.2 
73.2 
72.3 
73.7 
76.3 
76.6 
75.5 
76.6 
77.0 
76.9 
77.8 
77.1 
77.0 
77.4 
77.0 
Pareto Charts. In Exercises 11 and 12 construct the Pareto chart.
12.Getting a Job In a survey, subjects seeking a job were asked to whom they should send a thankyou note after having a job interview. Results were as follows: 40 said only the person they spent the most time with, 396 said everyone they met, 40 said only the most seniorlevel person, 15 said the person that they had the best conversation with, and 10 said that they don’t send thankyou notes (based on data from TheLadders.com). Comment on the results.
Pie Charts. In Exercises 13 and 14, construct the pie chart
Ch.3
Sec 31:
Critical Thinking. For Exercises 5–20, watch out for these little buggers. Each of these exercises involves some feature that is somewhat tricky. Find the (a) mean, (b) median, (c) mode, (d) midrange, and then answer the given question.
189,254,235,225,190,305,195,202,190,252,305
9.Hurricanes Listed below are the numbers of Atlantic hurricanes that occurred in each year. The data are listed in order by year, starting with the year 2000. What important feature of the data is not revealed by any of the measures of center?
8,9,8,7,9,15,5,6,8,4,12,7,8,2
19.California Smokers In the California Health Interview Survey, randomly selected adults are interviewed. One of the questions asks how many cigarettes are smoked per day, and results are listed below for 50 randomly selected respondents. How well do the results reflect the smoking behavior of California adults?
9 
10 
10 
20 
40 
50 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
In Exercises 21–24, find the mean and median for each of the two samples, then compare the two sets of results.
22.Parking Meter Theft Listed below are amounts (in millions of dollars) collected from parking meters by Brinks and others in New York City during similar time periods. A larger data set was used to convict five Brinks employees of grand larceny. The data were provided by the attorney for New York City, and they are listed on the Data and Story Library (DASL) website. Do the limited data listed here show evidence of stealing by Brinks employees?
Collection Contractor Was Brinks 
1.3 
1.5 
1.3 
1.5 
1.4 
1.7 
1.8 
1.7 
1.7 
1.6 
Collection Contractor Was Not Brinks 
2.2 
1.9 
1.5 
1.6 
1.5 
1.7 
1.9 
1.6 
1.6 
1.8 
In Exercises 29–32, find the mean of the data summarized in the frequency distribution. Also, compare the computed means to the actual means obtained by using the original list of data values, which are as follows: (Exercise 29) 36.2 years; (Exercise 30) 44.1 years; (Exercise31) 224.3; (Exercise 32) 255.1.
Age (yr) of Best Actress When Oscar Was Won 
Frequency 
20–29 
29 
30–39 
34 
40–49 
14 
50–59 
3 
60–69 
5 
70–79 
1 
80–89 
1 
Sec 32:
In Exercises 5–20, find the range, variance, and standard deviation for the given sample data. Include appropriate units (such as “minutes”) in your results. (The same data were used in Section 31, where we found measures of center. Here we find measures of variation.) Then answer the given questions.
89,91,55,7,20,99,25,81,19,82,60
189,254,235,225,190,305,195,202,190,252,305
13.Caffeine in Soft Drinks Listed below are measured amounts of caffeine (mg per 12oz of drink) obtained in one can from each of 20 brands (7UP, A&W Root Beer, Cherry Coke, . . ., Tab). Are the statistics representative of the population of all cans of the same 20 brands consumed by Americans?
0 0 34 34 34 45 41 51 55 36 47 41 0 0 53 54 38 0 41 47
In Exercises 21–24, find the coefficient of variation for each of the two samples; then compare the variation. (The same data were used in Section 31.)
Systolic: 
118 
128 
158 
96 
156 
122 
116 
136 
126 
120 
Diastolic: 
?80 
?76 
?74 
?52 
?90 
?88 
?58 
?64 
?72 
?82 
Single Line 
390 
396 
402 
408 
426 
438 
444 
462 
462 
462 
Individual Lines 
252 
324 
348 
372 
402 
462 
462 
510 
558 
600 
Identifying Significant Values with the Range Rule of Thumb. In Exercises 33–36, use the range rule of thumb to identify the limits separating values that are significantly low or significantly high.
Sec 33:
2.Heights The boxplot shown below results from the heights (cm) of males listed in Data Set 1 “Body Data” in Appendix B. What do the numbers in that boxplot tell us?
3.Boxplot Comparison Refer to the boxplots shown below that are drawn on the same scale. One boxplot represents weights of men, and the other boxplot represents weights of women. Which boxplot represents weights of women? Explain.
z Scores. In Exercises 5–8, express all z scores with two decimal places.
7.Female Pulse Rates Pulse rates of adult females are listed in Data Set 1 “Body Data” in Appendix B. The lowest pulse rate is 36 beats per minute, the mean of the listed pulse rates is
x¯=74.0
beats per minute, and their standard deviation is s = 12.5 beats per minute.
Significant Values. In Exercises 9 –12, consider a value to be significantly low if its z score is less than or equal to −2 or consider the value to be significantly high if its z score is greater than or equal to 2.
10.MCAT In a recent year, scores on the Medical College Admission Test (MCAT) had a mean of 25.2 and a standard deviation of 6.4. Identify the MCAT scores that are significantly low or significantly high.
Comparing Values. In Exercises 13–16, use z scores to compare the given values.
14.Red Blood Cell Counts Based on Data Set 1 “Body Data” in Appendix B, males have red blood cell counts with a mean of 4.719 and a standard deviation of 0.490, while females have red blood cell counts with a mean of 4.349 and a standard deviation of 0.402. Who has the higher count relative to the sample from which it came: a male with a count of 5.58 or a female with a count of 5.23? Explain.
15.Birth Weights Based on Data Set 4 “Births” in Appendix B, newborn males have weights with a mean of 3272.8 g and a standard deviation of 660.2 g. Newborn females have weights with a mean of 3037.1 g and a standard deviation of 706.3 g. Who has the weight that is more extreme relative to the group from which they came: a male who weighs 1500 g or a female who weighs 1500 g?
Boxplots. In Exercises 29–32, use the given data to construct a boxplot and identify the 5number summary.
30.Cell Phone Radiation Listed below are the measured radiation absorption rates (in W/kg) corresponding to these cell phones: iPhone 5S, BlackBerry Z30, Sanyo Vero, Optimus V, Droid Razr, Nokia N97, Samsung Vibrant, Sony Z750a, Kyocera Kona, LG G2, and Virgin Mobile Supreme. The data are from the Federal Communications Commission.
1.18, 1.41, 1.49, 1.04, 1.45, 0.74,0.89, 1.42, 1.45, 0.51, 1.38
32.Blood Pressure Measurements Fourteen different secondyear medical students at Bellevue Hospital measured the blood pressure of the same person. The systolic readings (mm Hg) are listed below.
138,130,135,140,120,125,120,130,144,143,140,130,150
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