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Chapter 8: Q.76 (page 520)
You have an SRS of observations from a Normally distributed population. What critical value would you use to obtain a confidence interval for the mean M of the population if S is unknown?
(a)
(b)
(c)
(d)
(e)
The correct option is (a).
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62. Blink When two lights close together blink alternately, we 鈥渟ee鈥� one light moving back and forth if the time between blinks is short. What is the
longest interval of time between blinks that preserves the illusion of motion? Ask subjects to turn a knob that slows the blinking until they 鈥渟ee鈥� two lights rather than one light moving. A report gives the results in the form 鈥渕ean plus or minus the standard error of the mean.鈥� Data for subjects are summarized as (in milliseconds).
(a) Find the sample standard deviation for these measurements. Show your work.
(b) Explain why the interval is not a confidence interval.
Alcohol abuse has been described by college presidents as the number one problem on campus, and it is an important cause of death in young adults. How common is it? A survey of 10,904 randomly selected U.S. college students collected information on drinking behavior and alcohol-related problems.9 The researchers defined 鈥渇requent binge drinking鈥� as having five or more drinks in row three or more times in the past two weeks. According to this definition, 2486 students were classified as frequent binge drinkers
Check conditions for constructing a confidence interval for the parameter
Price cuts (4.2) Stores advertise price reductions to attract customers. What type of price cut is most attractive? Experiments with more than one factor allow insight into interactions between the factors. A study of the attractiveness of advertised price discounts had two factors: percent of all foods on sale and whether the discount was stated precisely (as in, for example, off鈥�) or as a range (as in 鈥�to off鈥�). Subjects rated the attractiveness of the sale on a scale of 1 to 7. (a) Describe a completely randomized design using student subjects. (b) Explain how you would use the partial table of random digits below to assign subjects to treatment groups. Then use your method to select the first subjects for one of the treatment groups. Show your work clearly on your paper.
(c) The figure below shows the mean ratings for the eight treatments formed from the two factors. Based on these results, write a careful description of how percent on sale and precise discount versus range of discounts influence the attractiveness of a sale.
Gambling and the NCAA Gambling is an issue of great concern to those involved in college athletics. Because of this concern, the National Collegiate Athletic Association (NCAA) surveyed randomly selected student-athletes concerning their gambling-related behaviors.Of the Division I male athletes in the survey, reported participation in some gambling behavior. This includes playing cards, betting on games of skill, buying lottery tickets, betting on sports, and similar activities. A report of this study cited a % margin of error.
(a) The con铿乨ence level was not stated in the report. Use what you have learned to 铿乶d the con铿乨ence level, assuming that the NCAA took an SRS.
(b) The study was designed to protect the anonymity of the student-athletes who responded. As a result, it was not possible to calculate the number of students who were asked to respond but did not. How does this fact affect the way that you interpret the results?
The news article goes on to say: 鈥淭he theoretical errors do not take into account a margin of additional error resulting from the various practical difficulties in taking any survey of public opinion.鈥� List some of the 鈥減ractical difficulties鈥� that may cause errors in addition to the percentage point margin of error. Pay particular attention to the news article鈥檚 description of the sampling method.
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