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Chapter 10: Q 33. (page 644)
Which of the following is the correct margin of error for a confidence interval for the difference in the proportion of male and female college students who worked for pay last summer?
a.
b.
c.
d.
e.
Option (c) is correct.
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Coaching and SAT scores Let’s first ask if students who are coached increased their scores significantly, on average.
a. You could use the information on the Coached line to carry out either a two-sample t test comparing Try 1 with Try 2 or a paired t test using Gain. Which is the correct test? Why?
b. Carry out the proper test. What do you conclude?
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 α=0.05 significance level that the graduation rate among VLBW babies is less than for normal-birth-weight babies?
Which of the following will increase the power of a significance test?
a. Increase the Type II error probability.
b. Decrease the sample size.
c. Reject the null hypothesis only if the P-value is less than the significance level.
d. Increase the significance level .
e. Select a value for the alternative hypothesis closer to the value of the null hypothesis.
Suppose the true proportion of people who use public transportation to get to work in the Washington, D.C. area is . In a simple random sample of people who work in Washington, about how far do you expect the sample proportion to be from the true proportion?
a.
b.
c.
d.
e.
Final grades for a class are approximately Normally distributed with a mean of and a standard deviation of . A professor says that the topof the class will receive an A, the nexta B, the next a C, the next a D, and the bottom an F. What is the approximate maximum grade a student could attain and still receive an F for the course?
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