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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

Which of the following statements about the t distribution with degrees of freedom df is (are) true?

I. It is symmetric.

II. It has more variability than the t distribution with df+1degrees of freedom.

III. As df increases, the t distribution approaches the standard Normal distribution.

(a) I only (c) III only (e) I, II, and III

(b) II only (d) I and II

The P-value for the test in Question 5 is 0.0087. A correct interpretation of this result is that

(a) the probability that there is no linear relationship between an average number of putts per hole and total winnings for these 69players is 0.0087.

(b) the probability that there is no linear relationship between the average number of putts per hole and total winnings for all players on the PGA Tour’s world money list is 0.0087.

(c) if there is no linear relationship between an average number of putts per hole and total winnings for the players in the sample, the probability of getting a random sample of 69players yields a least-squares regression line with a slope of -4139198or less is 0.0087.

(d) if there is no linear relationship between an average number of putts per hole and total winnings for the players on the PGA Tour’s world money list, the probability of getting a random sample of 69 players yields a least-squares regression line with a slope of -4139198or less is 0.0087.

(e) the probability of making a Type II error is0.0087.

The body’s natural electrical field helps wounds heal. If diabetes changes this field, it might explain why people with diabetes heal more slowly. A study of this idea compared randomly selected normal mice and randomly selected mice bred to spontaneously develop diabetes. The investigators attached sensors to the right hip and front feet of the mice and measured the difference in electrical potential (in millivolts) between these locations. Graphs of the data for each group reveal no outliers or strong skewness. The computer output below provides numerical summaries of the data26.

The researchers want to know if there is evidence of a significant difference in mean electrical potentials between normal mice and mice with diabetes. Carry out a test using a 5%level of significance and report your conclusion.

Is wine good for your heart? A researcher from the University of California, San Diego, collected data on average per capita wine consumption and heart disease death rate in a random sample of 19 countries for which data were available. The following table displays the data.

(a) Is there statistically significant evidence of a negative linear relationship between wine consumption and heart disease deaths in the population of countries? Carry out an appropriate significance test at the α=0.05level.

(b) Calculate and interpret a 95% confidence interval for the slope β of the population regression line.

The swinging pendulum Refer to Exercise 33. Here is Minitab output from separate regression analyses of the two sets of transformed pendulum data:

Do each of the following for both transformations.

(a) Give the equation of the least-squares regression line. Define any variables you use.

(b) Use the model from part (a) to predict the period of a pendulum with length of 80 centimeters. Show your work.

(c) Interpret the value of s in context
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