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Chapter 10: Q 31. (page 643)
Let be the proportions of all college males and
females who worked last summer. The hypotheses to be tested are
a.
b.
c.
d.
e.
Option (a) is correct.
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A quiz question gives random samples of observations from each of two Normally distributed populations. Tom uses a table of t distribution critical values and degrees of freedom to calculate a confidence interval for the difference in the two population means. Janelle uses her calculator's two-sample t Interval with degrees of freedom to compute the confidence interval. Assume that both students calculate the intervals correctly. Which of the following is true?
(a) Tom's confidence interval is wider.
(b) Janelle's confidence Interval is wider.
(c) Both confidence Intervals are the same.
(d) There is insufficient information to determine which confidence interval is wider.
(e) Janelle made a mistake, degrees of freedom has to be a whole number.
Which of the following statements is false?
a. A measure of center alone does not completely summarize a distribution of quantitative data.
b. If the original measurements are in inches, converting them to centimeters will not change the mean or standard deviation.
c. One of the disadvantages of a histogram is that it doesn鈥檛 show each data value.
d. In a quantitative data set, adding a new data value equal to the mean will decrease the standard deviation.
e. If a distribution of quantitative data is strongly skewed, the median and interquartile range should be reported rather than the mean and standard deviation.
Stop doing homework! Researchers in Spain interviewed -year-olds about their homework habits鈥攈ow much time they spent per night on homework and whether they got help from their parents or not鈥攁nd then had them take a test with math questions and science questions. They found that students who spent between and minutes on homework did only a little better on the test than those who spent to minutes on homework. Beyond minutes, students who spent more time did worse than those who spent less time. The researchers concluded that to minutes per night is the optimum time for students to spend on homework.32 Is it appropriate to conclude that students who reduce their homework time from minutes to minutes will likely improve their performance on tests such as those used in this study? Why or why not? independent random samples from two populations of interest or from two groups in a randomized experiment, use two-sample t procedures for 渭1鈭捨�2
Shrubs and fire Fire is a serious threat to shrubs in dry climates. Some shrubs can
resprout from their roots after their tops are destroyed. Researchers wondered if fire would help with resprouting. One study of resprouting took place in a dry area of Mexico. The researchers randomly assigned shrubs to treatment and control groups. They clipped the tops of all the shrubs. They then applied a propane torch to the stumps of the treatment group to simulate a fire. All of the shrubs in the treatment group resprouted. Only of the shrubs in the control group resprouted.
a. State appropriate hypotheses for performing a significance test. Be sure to define the parameters of interest.
b. Check if the conditions for performing the test are met.
Starting in the , medical technology has enabled babies with very low birth weight (VLBW, less thangrams, or about 3.3 pounds) to survive without major handicaps. It was noticed that these children nonetheless had difficulties in school and as adults. A long-term study has followed 242 randomly selected VLBW babies to age years, along with a control group of 233 randomly selected babies from the same population who had normal birth weight.
a. Is this an experiment or an observational study? Why?
b. At age of the VLBW group and 193 of the control group had graduated from high school. Do these data provide convincing evidence at the 伪=0.05 significance level that the graduation rate among VLBW babies is less than for normal-birth-weight babies?
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