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Chapter 3: Q4 (page 127)
Sleep Variance The standard deviation of the sample values in Exercise 1 is 1.3 hours. What is the variance (including units)?
The variance is 1.7
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Weighted Mean A student of the author earned grades of A, C, B, A, and D. Those courses had these corresponding numbers of credit hours: 3, 3, 3, 4, and 1. The grading system assigns quality points to letter grades as follows: A = 4; B = 3; C = 2; D = 1; F = 0. Compute the grade-point average (GPA) and round the result with two decimal places. If the dean鈥檚 list requires a GPA of 3.00 or greater, did this student make the dean鈥檚 list?
In Exercises 5鈥�20, find the range, variance, and standard deviation for the given sample data. Include appropriate units (such as 鈥渕inutes鈥�) in your results. (The same data were used in Section 3-1, where we found measures of center. Here we find measures of variation.) Then answer the given questions.
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 5鈥�20, find the range, variance, and standard deviation for the given sample data. Include appropriate units (such as 鈥渕inutes鈥�) in your results. (The same data were used in Section 3-1, where we found measures of center. Here we find measures of variation.) Then answer the given questions.
Football Player Weights Listed below are the weights in pounds of 11 players randomly selected from the roster of the Seattle Seahawks when they won Super Bowl XLVIII (the same players from the preceding exercise). Are the measures of variation likely to be typical of all NFL players?
189 254 235 225 190 305 195 202 190 252 305
Critical Thinking. For Exercises 5鈥�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.
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 (FCC). The media often report about the dangers of cell phone radiation as a cause of cancer. The FCC has a standard that a cell phone absorption rate must be 1.6 W>kg or less. If you are planning to purchase a cell phone, are any of the measures of center the most important statistic? Is there another statistic that is most relevant? If so, which one?
1.18 1.41 1.49 1.04 1.45 0.74 0.89 1.42 1.45 0.51 1.38
Chebyshev鈥檚Theorem Based on Data Set 3 鈥淏ody Temperatures鈥� in Appendix B, body temperatures of healthy adults have a bell-shaped distribution with a mean of 98.20掳F and a standard deviation of 0.62掳F (using the data from 12 AM on day 2). Using Chebyshev鈥檚 theorem, what do we know about the percentage of healthy adults with body temperatures that are within 2 standard deviations of the mean? What are the minimum and maximum body temperatures that are within 2 standard deviations of the mean??
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