AnswersNC-Math 4 CRObservational Studies and Experiments

How to Experiment Well Answers

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A beauty product company conducts a study to test the effectiveness of a new shampoo to control split ends. One hundred subjects have volunteered to take part in the study, and will be split into a treatment group and a placebo group. The study leader will assign the subjects to the groups randomly using slips of paper. Which reason identifies why randomization is important?

A
It is important to make sure that groups have 50 people each.
B
It is important to make sure that the first 50 people to volunteer are not all in the same group.
C
It is important to make sure that people who do not currently have many split ends are placed in the placebo group.
D
It is important that subject characteristics such as hair length, hair color, and gender are distributed equally among the treatment groups.
2
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A beauty product company conducts a study to test the effectiveness of a new shampoo to control split ends. One hundred subjects have volunteered to take part in the study, and will be split into a treatment group and a placebo group. The study leader will randomly assign the subjects to the groups using slips of paper. How many slips of paper will the researcher need to draw in order to randomly assign subjects to the treatment groups?

A
2
B
25
C
50
D
100
3

A physician is testing the effectiveness of two new exercise plans on 70 subjects. To assign the subjects to the two treatment groups, he writes "Plan 1” on one slip of paper and "Plan 2” on another slip of paper. He randomly picks one of the slips, and assigns the first 35 subjects who signed up to that plan, and assigns the last 35 subjects to the other plan. Select the statement that best describes the composition of the treatment groups.

A
The treatment groups might not be comparable, because there is not a control group.
B
The treatment groups should be comparable, because there are a large number of subjects in each group.
C
The treatment groups should be comparable, because the exercise plan for each group was randomly selected.
D
The treatment groups might not be comparable, because the first 35 subjects to sign up for the study might share a characteristic related to exercise, such as high motivation.
4

A beauty product company conducts a study to test the effectiveness of a new shampoo to control split ends. One hundred subjects have volunteered to take part in the study and will be divided into a treatment group and a placebo group. The study leader will assign the subjects to the groups randomly using slips of paper. Select each statement that could describe an appropriate step in the labeling process.Write “treatment group” on 50 slips of paper and write “placebo group” on 50 slips of paper.Number the subjects from 1 to 100, and write the numbers 1 to 100 on the slips of paper.Write the name of each subject on a slip of paper.Write random one-digit numbers on 100 slips of paper.Use color-coding to distinguish the treatment group from the placebo group.

A
Write “treatment group” on 50 slips of paper and write “placebo group” on 50 slips of paper.
B
Number the subjects from 1 to 100, and write the numbers 1 to 100 on the slips of paper.
C
Write the name of each subject on a slip of paper.
D
Write random one-digit numbers on 100 slips of paper.
E
Use color-coding to distinguish the treatment group from the placebo group.
5

Select the correct random assignment using the table.

A
A: 0, 7, 5, 8, 1 B: 3, 4, 7, 2, 8
B
A: 0, 2, 4, 6, 8 B: 1, 3, 5, 7, 9
C
A: 0, 3, 6, 5, 8 B: 2, 9, 1, 7, 4
D
A: 0, 7, 5, 8, 1 B: 3, 4, 2, 6, 9
6

Which subjects will be in group A?

A
29, 17, 37, 20, 45, 27, 12, 23, 26, 25, 19, 30, 11, 27, 19
B
29, 17, 37, 20, 45, 27, 12, 23, 26, 25, 19, 30, 11, 28, 31
C
01, 02, 03, 04, 05, 06, 07, 08, 09, 10, 11, 12, 13, 14, 15
D
29, 07, 17, 20, 45, 27, 26, 40, 22, 01, 09, 23, 11, 22, 19
7

A candy manufacturer is testing new brands of sugar and needs to assign 150 recipes to two treatment groups. A table of random digits will be used to generate the sample. Select the appropriate way to number the experimental units.

A
000–149
B
1–150
C
01–75
D
1–2
8

A telemarketing company is conducting a study of new calling scripts. Seventy-five employees will be randomly assigned to three new scripts using a table of random digits. The study leader will assign the subjects to the groups using a table of random digits. How many unique two-digit numbers within the range of 01 to 75 will the study designer need to select from the table?

A
3
B
25
C
50
D
75
9

A telemarketing company is conducting a study of new calling scripts. A group of 75 employees will be randomly assigned to three new scripts. The study designer numbers the subjects from 01 to 75, and uses a table of random digits to select 50 unique, two-digit numbers in the range 01–75. The 25 subjects corresponding to the first 25 random two-digit numbers will be assigned to script 1, the second 25 to script 2, and the 25 remaining subjects to script 3. Select the statement that best describes the composition of the treatment groups.

A
The treatment groups should be comparable, because characteristics of the subjects should be roughly equivalent among the three groups.
B
The treatment groups should be comparable, because there are 25 subjects in each group.
C
The treatment groups should be comparable, because there are a relatively large number of subjects in each group.
D
The treatment groups will not be comparable.

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