Random assignment is part of a well-designed comparative experiment because

a. it is fairer 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

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

Step by step solution

01

Given information

Random assignment is part of a well-designed comparative experiment

02

Explanation

In a well-designed comparison experiment, we utilise random assignment because we want the different treatment groups to be as comparable as possible so that there are no differences between them before the treatment, and we can be sure that the differences are attributable to the treatments themselves.

As a result, option (b) is the best choice because it aids in the creation of roughly identical groups before the participants are subjected to treatments.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with Vaia!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

A Harris poll found that 54%of American adults don’t think that human beings developed from earlier species. The poll’s margin of error for 95%confidence was 3%. This means that

a. there is a 95%chance the interval (51%,57%) contains the true per cent of American adults who do not think that human beings developed from earlier species.

b. the poll used a method that provides an estimate within 3% of the truth about the population in 95%of samples.

c. if Harris conducts another poll using the same method, the results of the second poll will lie between 51%and 57%

d. there is a 3% chance that the interval is incorrect.

e. the poll used a method that would result in an interval that contains 54%in95% of all possible samples of the same size from this population.

T12.12 Foresters are interested in predicting the amount of usable lumber they can harvest from various tree species. They collect data on the diameter at breast height (DBH) in inches and the yield in board feet of a random sample of 20 Ponderosa pine trees that have been harvested. (Note that a board foot is defined as a piece of lumber 12 inches by 12 inches by 1 inch.) Here is a scatterplot of the data.

a. Here is some computer output and a residual plot from a least-squares regression on these data. Explain why a linear model may not be appropriate in this case.

The foresters are considering two possible transformations of the original data: (1) cubing the diameter values or (2) taking the natural logarithm of the yield measurements. After transforming the data, a least-squares regression analysis is performed. Here is some computer output and a residual plot for each of the two possible regression models:

b. Use both models to predict the amount of usable lumber from a Ponderosa pine with diameter 30 inches.
c. Which of the predictions in part (b) seems more reliable? Give appropriate evidence to support your choice.

Killing bacteria Expose marine bacteria to X-rays for time periods from 1to 15minutes. Here is a scatterplot showing the number of surviving bacteria (in hundreds) on a culture plate after each exposure time:


a. Below is a scatterplot of the natural logarithm of the number of surviving bacteria versus time. Based on this graph, explain why it would be reasonable to use an exponential model to describe the relationship between the count of bacteria and the time.


b). Here is the output from a linear regression analysis of the transformed data. Give the equation of the least-squares regression line. Be sure to defne any variables you use.

c. Use your model to predict the number of surviving bacteria after 17minutes.

T12.10We record data on the population of a particular country from 1960 to 2010. A
scatterplot reveals a clear curved relationship between population and year. However, a different scatterplot reveals a strong linear relationship between the logarithm (base 10) of the population and the year. The least-squares regression line for the transformed data is
log(population)=^13.5+0.01(year)
Based on this equation, which of the following is the best estimate for the population of the country in the year 2020?
a. 6.7
b. 812
c. 5,000,000
d. 6,700,000
e. 8,120,000

Boyle's law If you have taken a chemistry or physics class, then you are probably familiar with Boyle's law: for gas in a confined space kept at a constant temperature, pressure times volume is a constant (in symbols, PV=kPV=k). Students in a chemistry class collected data on pressure and volume using a syringe and a pressure probe. If the true relationship between the pressure and volume of the gas is PV=k,PV=k, then

P=k1VP=k1V

Here is a graph of pressure versus a volume, 1volume, along with output from a linear regression analysis using these variables:

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 pressure in the syringe when the volume is 17cubic centimeters.

See all solutions

Recommended explanations on Math Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.

Sign-up for free