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The Practice of Statistics for AP

David Moore,Daren Starnes,Dan Yates

$Math Studyset Vaia Explanations$ Math

4th Edition · 809 pages

ISBN: 9781319113339

Chapter 12: Q. 20 (page 802)

Random assignment is part of a well-designed comparative experiment because
(a) It is more fair to the subjects.
(b) It helps create roughly equivalent groups before treatments are imposed on the subjects.
(c) It allows researchers to generalize the results of their experiment to a larger population.
(d) It helps eliminate any possibility of bias in the experiment.
(e) It prevents the placebo effect from occurring

Short Answer

Expert verified

Correct option is (b), It helps create roughly equivalent groups before treatments are imposed on the subjects.

Step by step solution

01

Given

We need to explain reason of random assignment as part of well-designed comparative experiment.

02

Step 2:Explanation

In experimental research,random assignment is a way of placing participants from your sample into different treatment groups using randomization.

Random assignment is part of comparative experiment as it helps you ensure that all groups are comparable at the start of a study, any differences between them are due to random factors.

Hence, option (b) is correct answer.

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Most popular questions from this chapter

Women who are severely overweight suffer enormous social and economic consequences, a new study has shown. They are $20 %$ less likely to marry, they have household incomes that are an average of $$ 6710$ lower, and they are $10 %$ more likely to live in poverty. The findings are from an eight-year observational study of $10, 039$ randomly selected women who were $16$ to $24$ years old when the research began. Does this study give strong evidence that being severely overweight causes a woman to have a lower income?

(a) Yes. The study included both women who were severely overweight and women who were not. (b) Yes. The subjects in the study were selected at random.

(c) No. The study showed that there is no connection between income and being severely overweight.

(d) No. The study suggests an association between income and being severely overweight, but we can’t draw a cause-and-effect conclusion.

(e) There is not enough information to answer this question.

Park rangers are interested in estimating the weight of the bears that inhabit their state. The rangers have data

on weight (in pounds) and neck girth (distance around the neck in inches) for 10 randomly selected bears. Some

regression output for these data is shown below.

Which of the following represents a 95% confidence interval for the true slope of the least-squares regression line relating the weight of a bear and its neck girth?

$(a) 241.710 \pm 38.57 (b) 241.70 \pm 88.94 (c) 20.230 \pm 1.695 (d) 20.230 \pm 3.83 (e) 20.230 \pm 3.91$

Suppose that the mean weight of a certain type of pig is $280 p o u n d s$ with a standard deviation of $80 p o u n d s$ . The weight distribution of pigs tends to be somewhat skewed to the right. A random sample of $100$ pigs is taken. Which of the following statements about

the sampling distribution of the sample mean weight $x$ is true?

(a) It will be Normally distributed with a mean of $280 p o u n d s$ and a standard deviation of $80 p o u n d s .$

(b) It will be Normally distributed with a mean of $280 p o u n d s$ and a standard deviation of $8 p o u n d s .$

(c) It will be approximately Normally distributed with a mean of $280 p o u n d s$ and a standard deviation of $80 p o u n d s .$

(d) It will be approximately Normally distributed with a mean of $280 p o u n d s$ and a standard deviation of $8 p o u n d s .$

(e) There is not enough information to determine the mean and standard deviation of the sampling distribution.

An experimenter wishes to test whether or not two types of fish food (a standard fish food and a new product) work equally well at producing fish of equal weight after a two-month feeding program. The experimenter has two identical fish tanks (1 and 2) to put fish in and is considering how to assign $40 f i s h$ , each of which has a numbered tag, to the tanks. The best way to do this would be to

(a) put all the odd-numbered fish in one tank, the even in the other, and give the standard food type to the odd-numbered ones.

(b) obtain pairs of fish whose weights are virtually equal at the start of the experiment and randomly assign one to Tank 1 and the other to $T a n k 2$ , with the feed assigned at random to the tanks.

(c) proceed as in part (b), but put the heavier of the pair into $T a n k 2$ .

(d) assign the fish at random to the two tanks and give the standard feed to $T a n k 1$ .

(e) not proceed as in part (b) because using the initial weight in part (b) is a nonrandom process. Use the initial length of the fish instead.

An old saying in golf is “You drive for show and you putt for dough.” The point is that good putting is more important than long driving for shooting low scores and hence winning money. To see if this is the case, data from a random sample of $69$ of the nearly $1000$ players on the PGA Tour’s world money list are examined. The average number of putts per hole and the player’s total winnings for the previous season is recorded. A least-squares regression line was fitted to the data. The following results were obtained from statistical software.

Suppose that the researchers test the hypotheses $H_{0} : β = 0$ : $H_{a} : β < 0$ . The value of the t statistic for this test is

(a) $2.61$

(b) $2.44$

(c) $0.081$

(d) $- 2.44$

(e) $- 20.24$

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