Section 1.6 Homework

1. Define the following terms.

​(a)	Experimental unit		​(d)	Factor
​(b)	Treatment		​(e)	Placebo
​(c)	Response variable		​(f)	Confounding

​(a)  Define experimental unit. Choose the correct answer below.

1. Any combination of the values of the factors​ (explanatory variables)
2. The quantitative or qualitative variable for which the experimenter wishes to determine how its value is affected by the explanatory variable
3. A​ person, object, or some other​ well-defined item upon which a treatment is applied
4. An innocuous​ medication, such as a sugar​ tablet, that​ looks, tastes, and smells like the experimental medication

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(b)  Define treatment. Choose the correct answer below.

1. The number of individuals in the experiment
2. The quantitative or qualitative variable for which the experimenter wishes to determine how its value is affected by the explanatory variable
3. Any combination of the values of the factors​ (explanatory variables)
4. A controlled study to determine the effect varying one or more explanatory variables or factors has on a response variable

​

(c)  Define response variable. Choose the correct answer below.

1. The effect of two factors​ (explanatory variables on the response​ variable) cannot be distinguished.
2. The quantitative or qualitative variable for which the experimenter wishes to determine how its value is affected by the explanatory variable
3. The variable whose effect on the response variable is to be assessed by the experimenter
4. An innocuous​ medication, such as a sugar​ tablet, that​ looks, tastes, and smells like the experimental medication

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(d)  Define factor. Choose the correct answer below.

1. A controlled study to determine the effect varying one or more explanatory variables or factors has on a response variable
2. A variable whose effect on the response variable is to be assessed by the experimenter
3. Grouping together similar experimental units
4. An innocuous​ medication, such as a sugar​ tablet, that​ looks, tastes, and smells like the experimental medication​

 

(e)  Define placebo. Choose the correct answer below.

1. An innocuous​ medication, such as a sugar​ tablet, that​ looks, tastes, and smells like the experimental medication
2. A controlled study to determine the effect varying one or more explanatory variables or factors has on a response variable
3. Grouping together similar experimental units
4. Using treatments on many experimental units

​

(f)  Define confounding. Choose the correct answer below.

1. A controlled study to determine the effect varying one or more explanatory variables or factors has on a response variable
2. Grouping together similar experimental units
3. Using treatments on many experimental units
4. The effect of two factors​ (explanatory variables on the response​ variable) cannot be distinguished.

 

2.  What is replication in an​ experiment?  Choose the correct answer below.

1. Replication is applying each treatment to more than one experimental unit.
2. Replication is randomly assigning each experimental unit to a treatment.
3. Replication is grouping together similar experimental units and then using random assignment.
4. Replication is pairing up related experimental units.

 

3.  Explain the difference between a​ single-blind and a​ double-blind experiment.  Choose the correct answer below.

1. A single blind experiment is one in which each experimental unit is randomly assigned to a treatment. A​ double-blind experiment is one in which similar experimental units are grouped together and the experimental units within each block are randomly assigned to treatments.
2. In a​ single-blind experiment, the subject does not know which treatment is received. In a​ double-blind experiment, neither the subject nor the researcher in contact with the subject knows which treatment is received.
3. In a​ single-blind experiment, the researcher does not know what the response variable is. In a​ double-blind experiment, neither the subject nor the researcher knows what the response variable is.
4. In a​ single-blind experiment, there is a control group. In a​ double-blind experiment, there is both a control group and a placebo treatment is used.

 

4.   Grouping together similar experimental units and then randomly assigning the experimental units within each group to a treatment is called _____

5.  Determine whether the following statement is true or false.  ​Generally, the goal of an experiment is to determine the effect that the treatment will have on the response variable.  Choose the correct answer below.

1. True
2. False

 

6.  To determine if topiramate is an effective treatment for alcohol​ dependence, researchers conducted a​ 14-week trial of 371 men and women aged 18 to 65 years diagnosed with alcohol dependence. In this​ doubleblind, randomized,​ placebo-controlled experiment, subjects were randomly given either 300 milligrams​ (mg) of topiramate​ (183 subjects) or a placebo​ (188 subjects)​ daily, along with a weekly compliance enhancement intervention. The variable used to determine the effectiveness of the treatment was​ self-reported percentage of heavy drinking days. Results indicated that topiramate was more effective than placebo at reducing the percentage of heavy drinking days. The researchers concluded that topiramate is a promising treatment for alcohol dependence. Complete parts​ (a) through​ (f).

​(a) What does it mean for the experiment to be​ placebo-controlled?

1. The experiment will have a placebo group that takes no medication. This placebo group serves as a baseline treatment that can be used to compare to the group that is actually taking medication.
2. The experiment will have a control group that takes a​ placebo, which is a lesser dose of the medication. This control group serves as a baseline treatment that can be used to compare to the group that is taking the full dose of the medication.
3. The experiment will have a control group that takes a​ placebo, which is a innocuous​ medication, such as a sugar tablet. This control group serves as a baseline treatment that can be used to compare to the group that is actually taking the medication.
4. The experiment will have a placebo group which will study the group that is actually taking the medication.

​

(b) What does it mean for the experiment to be​ double-blind? Why do you think it is necessary for the experiment to be​ double-blind?  ​First, explain what it means for the experiment to be​ double-blind. Choose the correct answer below.

1. Only the subject knows which treatment the subject is receiving.
2. Both the subject and the researcher know which treatment the subject is receiving.
3. Only the researcher knows which treatment the subject is receiving.
4. Neither the subject nor the researcher knows which treatment the subject is receiving.

 

Why do you think it is necessary for the experiment to be​ double-blind?

1. The experiment is​ double-blind to ensure that any observed effects of the treatment is not due to some characteristic of a single experimental unit.
2. The experiment is​ double-blind so that the individual monitoring the subjects can better distinguish the effects of the medication from the effects of the placebo.
3. The experiment is​ double-blind so that the subjects receiving the medication know that they are not in the placebo group and can act accordingly.
4. The experiment is​ double-blind so that the subjects receiving the medication do not behave differently and so the individual monitoring the subjects does not treat those receiving medication differently from those receiving a placebo.

 

(c) What does it mean for the experiment to be​ randomized?

1. It means that the subjects are randomly selected from all of the people in the area of the study.
2. It means that the different dosage levels of the placebo are randomly assigned to individuals that are not taking the medication.
3. It means that the subjects are randomly assigned to take either the topiramate or the placebo.
4. It means that the different dosage levels of the medication are randomly assigned to individuals that are not taking the placebo.

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(d) What is the population for which this study​ applies? What is the​ sample?

1. The population is 371 men and women aged 18 to 65 years diagnosed with alcohol dependence. The sample is all​ 18-65 year olds with alcohol dependence.
2. The population is 371 men and women aged 18 to 65 years diagnosed with alcohol dependence. The sample is all​ 18-65 year olds.
3. The population is all​ 18-65 year olds. The sample is 371 men and women aged 18 to 65 years diagnosed with alcohol dependence.
4. The population is all​ 18-65 year olds with alcohol dependence. The sample is 371 men and women aged 18 to 65 years diagnosed with alcohol dependence.

 

​(e) What are the​ treatments?

1. 300 mg of topiramate daily and a weekly compliance enhancement intervention
2. 300 mg of topiramate daily
3. A weekly compliance enhancement intervention
4. 300 mg of topiramate or a placebo​ daily, and a weekly compliance enhancement intervention

 

​(f) What is the response​ variable?

1. Percentage of heavy drinking days
2. Test score at the weekly compliance enhancement intervention
3. Amount of medication consumed
4. Amount of placebo consumed

 

7. A school psychologist wants to test the effectiveness of a new method of teaching Spanish.  She recruits 500 second​-grade students and randomly divides them into two groups. Group 1 is taught by means of the new​ method, while group 2 is taught by traditional methods. The same teacher is assigned to teach both groups. At the end of the​ year, an achievement test​ (graded on a scale from​ 1-10) is administered and the results of the two groups are compared. Complete parts​ (a) through​ (i) below.

​(a) What is the response variable in this​ experiment?

1. The score of group 2 on the achievement test
2. The​ students’ ability in Spanish
3. The score of group 1 on the achievement test
4. The scores on the achievement tests of both group 1 and group 2

 

​(b) Is the response variable qualitative or​ quantitative?

1. The response variable is qualitative because it is a measurement.
2. The response variable is qualitative because it is a characteristic.
3. The response variable is quantitative because it is a characteristic.
4. The response variable is quantitative because it is a measurement.

 

​(c) Which of the following explanatory variables is​ manipulated?

1. Method of teaching
2. Teacher
3. School district
4. Grade level

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(d) What are the​ treatments? How many treatments are​ there?

1. The treatments are the new teaching method and the traditional teaching method. There are 2 treatments.
2. The treatment is the teacher. There is 1 treatment.
3. The treatments are group 1 and group 2. There are 2 treatments.
4. The treatments are the students. There are 500 treatments.

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(e) How are the factors that are not controlled dealt​ with?

1. By assigning the first half of the second​-grade students to group 1 and the other half to group 2
2. Random assignment
3. The groups are split based on their teacher.
4. By assigning the first half of the second​-grade students to group 2 and the other half to group 1

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(f) Which group serves as the control​ group?

1. Group 1 serves as the control group because this group corresponds to the new teaching method that is being tested.
2. Group 2 serves as the control group because this group corresponds to the new teaching method that is being tested.
3. Group 1 serves as the control group because this group corresponds to the standard method that will be compared to the other method.
4. Group 2 serves as the control group because this group corresponds to the standard method that will be compared to the other method.

 

​(g) What type of experimental design is​ this?

1. ​Matched-pairs design
2. ​Case-control study
3. Completely randomized design
4. Randomized block design

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(h) Identify the subjects.

1. The school district
2. The teachers
3. All second​-grade students in the school district
4. The 500 students

 

8. A physician wanted to compare two types of headache relief. One type is medication and the other is using pressure points. It is a common belief that medication relieves pain faster. This belief is tested by having 10 migraine sufferers compare both types of pain relief and record their observations on a standardized scale of response. A coin flip was used to determine which type of headache relief each individual would try first.  Results indicated that there was no difference in the two types of pain relief. Complete parts​ (a) through​ (f) below.

​(a) What type of experimental design is​ this?

1. ​Case-control study
2. Completely randomized design
3. Randomized block design
4. ​Matched-pairs design

 

​(b) What is the response variable in this​ study?

1. The types of pain relief
2. The migraine sufferers
3. The recorded observations
4. The coin flip

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(c) What is the factor that is set to predetermined​ levels? What is the​ treatment?

1. The factor is the migraine sufferers. The treatments are the 10 different migraine sufferers.
2. The factor is the type of pain relief. The treatments are medication and using pressure points.
3. The factor is the coin flip. The treatments are heads and tails.
4. The factor is the recorded observations. The treatments are medication and using pressure points.

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(d) Identify the experimental units. Choose the correct answer below.

1. The types of pain relief
2. The migraine sufferers
3. The coin flip
4. The recorded observations

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(e) Why is a coin used to decide the headache relief each individual would try first​?

1. To introduce an element of chance into the experiment
2. To eliminate bias as to which pain relief was used first
3. To show that the experiment is fair
4. None of the above

 

9  A researcher has decided to test the effectivness of a drug meant to reduce high cholesterol through a completely randomized design. She has obtained 9 volunteers with high​ cholesterol: Amanda,​ Brian, Christine,​ David, Emily,​ Fred, George,​ Heather, and Ivan. Number the volunteers 1 through​ 9, alphabetically. Use the third row of digits in the random number table below to randomly assign 3 of the volunteers to the experimental group​ (ignore zeros). The remaining volunteers will go into the control group. List the individuals in each group.

What are the numbers of the three volunteers​ selected? _______ ​(List the terms in the same order they appear in the original​ list.)

List the three indivduals assigned to the experimental group. Choose the correct answer below.

1. Ivan, David, Christine
2. Heather, David, Fred
3. Heather, David, Christine
4. Heather, Amanda, Christine

 

List the remaining indivduals assigned to the control group. Choose the correct answer below.

1. Ivan, Amanda, Brian, Fred, Emily, George
2. Heather, David, Christine
3. Ivan, Amanda, Brian, Fred, Emily, David

 

 

10. You wonder whether green tea lowers cholesterol. Complete parts​ (a) through​ (h) below.

​(a) To research the claim that green tea lowers LDL​ (so-called bad)​ cholesterol, you ask a random sample of individuals to divulge whether they are regular green tea users or not. You also obtain their LDL cholesterol levels.​ Finally, you compare the LDL cholesterol levels of the green tea drinkers to those of the​ non-green tea drinkers. Explain why this is an observational study.

1. This is an observational study because there is no intent to manipulate the explanatory​ variable, whether the individual is a green tea drinker or not.
2. This is an observational study because the researcher is manipulating the explanatory​ variable, LDL cholesterol levels.
3. This is an observational study because there is no intent to manipulate the explanatory​ variable, LDL cholesterol levels.
4. This is an observational study because the researcher is manipulating the explanatory​ variable, whether the individual is a green tea drinker or not.

​(b) Name some lurking variables that might exist in the study. Select all that apply.

1. Exercise
2. Gender
3. Genetics
4. Number of siblings
5. Age
6. Diet

 ​(c)​ Suppose, instead of surveying individuals regarding their​ tea-drinking habits, you decide to conduct a designed experiment. You identify 120 volunteers to participate in the study and decide on three levels of the​ treatment: a​ placebo, one cup of green tea​ daily, two cups of green tea daily. The placebo is a drink that​ looks, tastes, and smells like green tea. The experiment is to run for one year. The response variable will be the change in LDL cholesterol for each subject from the beginning of the study to the end. What type of experimental design is​ this?

1. ​Matched-pairs design
2. ​Case-control study
3. Completely randomized design
4. Randomized block design​

(d) Explain how you would use blinding in this experiment.

1. Do not allow the​ researcher(s) giving the treatments to know which level of the treatment they are giving. This is a​ single-blind study.
2. Do not allow the subjects to know which level of the treatment they are receiving. This is a​ double-blind study.
3. Do not allow the subjects to know which level of the treatment they are receiving.​ Also, do not allow the​ researcher(s) giving the treatments to know which level of the treatment they are giving. This is a​ double-blind study.
4. Split up both the males and females equally into the three different treatment groups.
5. E.Blinding is not possible in this experiment.

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(e) What is the​ factor? Is it qualitative or​ quantitative?

The factor is ______

It is _________

 

 (f) What factors might you attempt to control in this​ experiment? Select all that apply.

1. Diet
2. Exercise
3. Age
4. Gender
5. Genetics
6. Number of siblings

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(g) Explain how to use randomization in this experiment. How does randomization neutralize those variables that are not​ controlled?

Randomly assign the ___________to treatment groups. This will mute the effect of variation attributable to the that are not controlled. Then any difference in the value of the response variable among the different treatment groups is a result of _______________

 

 (h) Suppose you assigned 40 subjects to each of the three treatment groups. In​ addition, you decided to control the variable exercise by having each subject perform 150 minutes of cardiovascular exercise each week by walking on a treadmill.​ However, the 40 subjects in the placebo group decided they did not want to walk on the treadmill and skipped the weekly exercise. Explain how exercise is now a confounding variable.

Any difference in the change in the ___________cannot be attributed to the ___________.  It may be the

that caused the change in the _______