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Homework answers / question archive / Question1)Depression is a mental disorder that that affects many people
Question1)Depression is a mental disorder that that affects many people. To investigate whether the drug Zoloft can reduce depression, a study by NIH gave the drug to 250 depression sufferers and the placebo to another 250. Neither doctors nor patients were told who received the drug. The number of episodes of depression reported by each subject was recorded. This is an example of
Question 2
Employees at a large telephone company are asked about the status of their health insurance status. Employees are coded as “1” if health insurance is obtained through the telephone company's benefit program, “2” if it obtains health insurance from another source (e.g., through a spouse's employment benefit program), or “0” if the employee does not have health insurance. The variable class standing is
Question 3
A group of research scientists emailed 530 randomly selected registered voters in an Arizona city. They asked respondents to give an opinion about the job performance of Hilary Clinton. Of the 530 surveys sent out, 87 are returned, and of these, only 15 say they're satisfied with how Hilary Clinton is doing. The population is
Question 4
The ages of 18 faculty members in a college psychology department is depicted in the plot below. 43 represents 43 years. If the faculty member with the highest age retires and is replaced by a 26yearold, the median age will
Students (sample size =100) were in a class that took a Psychology exam. The grades on the test are summarized in the frequency table below. Which of the following intervals is the median grade in?

Grade 
Frequency 

91–100 
11 

81–90 
31 

71–80 
42 

61–70 
16 
Question 6
A sample of the percent increase in the growth of five dogs over a oneyear period:
8.9% 12.2% 13.7% 14.4% 9.8%
The mean percent increase in this sample is
Question 7
You calculate the number of spots on a pair of two dice that you roll, sides facing up (the total can be called “X”). This is also assuming the dice are not loaded (fair). The probability that X is at least 7 is
Question 8
St. Bernard’s birthweights at a local hospital have a Normal distribution with a mean of 110 oz and a standard deviation of 15 oz.
The proportion of St. Bernard puppies with birthweights between 125 oz and 140 oz is:
Question 9
A company employs a large number of students to do data entry into the same computer. The time taken for new students to learn the computer system is known to have a Normal distribution with a mean of 130 minutes and a standard deviation of 20 minutes. A potential student worker is automatically hired if he or she learns the computer system in less than 100 minutes. A cutoff time is set at the slowest 40% of the learning distribution. Anyone slower than this cutoff time is not hired.
The proportion of new students that take under two hours to learn the system is:
Question 10
Nabisco produces packets of oyster crackers labeled “Giant Size 32 Ounces.” The actual weight of the oyster crackers in such a box has a Normal distribution with a mean of 33 oz and a standard deviation of 0.7 oz. To avoid having dissatisfied customers, Nabisco says a box of crackers is considered underweight if it weighs less than 32 oz. To avoid losing money, it labels the top 5% (the heaviest 5%) overweight.
What proportion of Nabisco oyster cracker boxes is underweight (i.e., weigh less than 32 oz)?
Question 11
You plan to construct a confidence interval for the mean μ of a Normal population with (known) standard deviation σ. Which of the following will reduce the size of the margin of error?
Question 12
A simple random sample of 1000 American adults found that the average number of hours spent watching television during a typical week was 13.8. A simple random sample of 500 Canadians yielded an average of 12.5 hours per week of television viewing. Assume that the American and Canadian distributions for weekly television, viewing times have the same standard deviations. The sampling variability associated with the sample means (described in this problem) is
Question 13
Suppose we are sampling large bags of skittles and testing the null hypothesis that the mean number of red skittles is 20 (H_{0}: μ = 20) and the alternative hypothesis that the mean number of red skittles is not 20 (H_{a}: μ ≠ 20, for a normal population with σ = 5. A random sample of 25 observations of skittles are drawn from the population, and we find the sample mean of these observations is equal to 17.6. The Pvalue is closest to
Question 14
Is the mean age at which children in Europe can first read now under 4 years? If the population of all children in Europe has a mean age of μ years until they begin to read, one would test which of the following null and alternative hypotheses to answer this question?
Question 15
A researcher has developed a new drug designed to increase health. In an experiment, 21 subjects were assigned randomly to the treatment group, and received the new health drug. The other 23 subjects were assigned to the control group, and received no treatment. After a suitable period of time, the reduction in health for each subject was recorded. A summary of these data is:


n 
Sample mean 
s 

Treatment group (new health drug): 
21 
23.48 
8.01 

Control group (no health drug): 
23 
18.52 
7.15 
The researcher suspects that the new health drug results in greater average reduction unhealthy behaviors than no drug does. Based on these data, the computed twosample t statistic is
Question 16
There is pesticide banned in the United States for its danger to living things called DDT. In an experiment, 6 mice were exposed to DDT poisoning and 6 mice were not. For each mouse in the experiment, a measurement of their body sensitivity was recorded. The researchers suspected that the mean body sensitivity for mice exposed to DDT is greater than that for mice not poisoned. The data follow:
Mice with DDT: 
12.207 
16.869 
25.050 
22.429 
8.456 
20.589 
Mice without DDT: 
11.074 
9.686 
12.064 
9.351 
8.182 
6.642 
Let mu 1 be the mean body sensitivity for mice given DDT. Let mu 2 be the mean body sensitivity for mice not given DDT.
Which of the following is a reasonable conclusion?
Question 17
A study was conducted to assess the effect of a drug on the treatment of patients with depression. The three treatment groups were a control, a low dose of 1.5 mg per kilogram of body weight, and a high dose of 3 milligrams per kilogram of body weight. There were seventy subjects, with thirty assigned at random to the control and twenty to each of the treatments. Subjects were classified as responders or nonresponders to treatment based on a battery of psychological tests that were administered.
The overall proportion of responders in the experiment is
Question 18
Do women and men treat female and male kids differently? An observational study was conducted near the reptile exhibit at the Phoenix Zoo on weekends in 1997. The data are from 39 groups of three—one adult female, one adult male, and one toddler, in which the toddler was being carried. Recorded below is which adult (male or female) was carrying the toddler by the sex of the toddler.

Sex of toddler 

Sex of adult carrying toddler 
Male 
Female 
Male 
8 
17 
Female 
6 
8 
The proportion of times a male adult was carrying the toddler is:
Question 19
A random sample of Ohio voters was asked about the number of cars or trucks they own (one, two, or at least three) and the type of community they lived in (rural, suburban, urban). The twoway table follows.

Community Type 

Number of cars 
Rural 
Suburban 
Urban 
One 
120 
230 
530 
Two 
470 
620 
390 
At least three 
335 
420 
85 
The degrees of freedom for the chisquare test for this twoway table are:
Question 20
The volume of oxygen consumed (in liters per minute) while a person is at rest and while he or she is exercising (running on a treadmill) was measured for each of 50 subjects. The goal is to determine if the volume of oxygen consumed during aerobic exercise can be estimated from the amount consumed at rest. The results are plotted below.
In this study, the explanatory variable is
Question 21
Due to erosion, a river shoreline is losing several thousand pounds of soil each year. A linear equation that expresses the total amount of soil lost per year is y = 12,000x.
What is the yintercept?
Question 22
A researcher states that bone density in women is negatively associated with age. This means that
Question 23
A researcher is studying treatments for agoraphobia with panic disorder. The treatments are to be the drug Imipramine at the two doses 1.5 mg per kg of body weight and 2.5 mg per kg of body weight. There will also be a control group given a placebo. Thirty patients were randomly divided into three groups of ten each. One group was assigned to the control, and the other two groups were assigned to the two drug treatments. After twentyfour weeks on treatment, each of the subject's symptoms were evaluated through a battery of psychological tests, where high scores indicate a lessening of symptoms. Assume the data for the three groups are independent and approximately Normal with the same variance. An ANOVA F test tested the null hypothesis that there were no differences among the means for the three treatments that had a Pvalue less than 0.001. Which conclusion is correct?


Question 24
An ANOVA F test is an extension of a
Question 25
A manufacturer of infant formula is running an experiment using the standard (control) formulation and two new formulations, A and B. The goal is to boost the immune system in young children. There are 120 children in the study, and they are randomly assigned, 40 to each of the three feeding groups. The study is run for twelve weeks. The variable measured is Total IGA in mg per dl. It is measured at the end of the study, with higher values being more desirable. We are going to run a oneway ANOVA on these data. The hypotheses tested by the oneway ANOVA F test are
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