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Question: Reuters (June 24, 1997) reported on a study published in the Journal of the American Medical Association (1997, vol. 277, pp. 1940-1944) in which researchers recruited 276 volunteers (aged 18 to 55) and used nose drops to infect them with a cold virus. The volunteers were then quarantined and observed to see whether they came down with a cold or infection. They also answered questions about their social lives, including the number of different types of contacts they had (family, work, community, religious groups, and so on). Reuters reported that "those with one to three types of social contacts were 4.2 times as likely to come down with cold symptoms and signs of infection compared to those with six or more contacts."
a. Explain why this is an observational study, not a randomized experiment.
b. What were the explanatory and response variables of interest to the researchers?
c. The researchers in this study took an unusual step to help reduce the impact of confounding variables. Explain what they did and why it might have helped to reduce the impact of confounding variables.
Response variable = Child's IQ at age 10; explanatory variable = whether mother smokes or not; confounding variable = mother's educational level.
Conduct a statistical test to determine whether there is a significant difference between average men's and women's ratings of prime-time television programs.
A portion of a study by Wechsler (1958) reports that for 100 males taking the Wechsler Adult Intelligence Scale (WAIS), the sample mean and variance on picture completion are X‾= 9.79 and s = 2.72. Test the hypothesis H0:µ ≥ 10.5 with α = .025.
what is the probability of generating a password with all lowercase letters if a password consists of eight characters
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in a study of pregnant women and their ability to correctly predict the sex of their baby 58 of the pregnant women had
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Produce a 95% confidence interval to estimate the change of the average selling price of gasoline between the twentieth and the twenty-first centuries.
Find the critical values and identify the rejection regions. Calculate d and sd. Use the t-test to find the standardized test statistic t. decide whether to reject or fail to reject the null hypothesis.
Wendy and Tim have invited 400 family and friends to their wedding. The couple would like to randomly choose 20 of these guests to give their reception.
Firing pottery. A ceramics factory can fire eight large batches of pottery a day. Sometimes a few of the pieces break in the process.
What is the probability that a home has a garage but not a swimming pool?
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