Chapter 1. Subjects, Factors, Treatments

Incorrect. In an experiment, the treatment is applied on the subject.

Correct. In an experiment, the treatment is applied on the subject.

Incorrect. Try again.

2

Incorrect. The response to the treatment is measured at the end of the study.

Correct. The response to the treatment is measured at the end of the study.

Incorrect. Try again.

2

Incorrect. Some students mistakenly think that the mean or the proportion of the responses in a treatment group is the measurement of the response variable. But the response is measured on the individual, never on a group of individuals.

Correct. Some students mistakenly think that the mean or the proportion of the responses in a treatment group is the measurement of the response variable. But the response is measured on the individual, never on a group of individuals.

Incorrect. Try again.

2

Incorrect. This is a correct statement.

Correct. This is a correct statement.

Incorrect. Try again.

2

Incorrect. This is a correct statement.

Correct. This is a correct statement.

Incorrect. Try again.

2

Incorrect. This is a correct statement.

Correct. This is a correct statement.

Incorrect. Try again.

2

Incorrect. A field is not the individual for two reasons. First, each field is divided into thirds and second, because three treatments are applied on each field, not just one.

Correct. A field is not the individual for two reasons. First, each field is divided into thirds and second, because three treatments are applied on each field, not just one.

Incorrect. Try again.

2

Incorrect. Since three test fertilizers are to be compared, the treatments are the three test fertilizers.

Correct. Since three test fertilizers are to be compared, the treatments are the three test fertilizers.

Incorrect. Try again.

2

Incorrect. First of all, the explanatory variable is a phrase describing all possible treatments. Since the treatments are the three test fertilizers, the explanatory variable is which of the three test fertilizers is applied to the plot. So, we state the explanatory variable as "type of fertilizer."

Correct. First of all, the explanatory variable is a phrase describing all possible treatments. Since the treatments are the three test fertilizers, the explanatory variable is which of the three test fertilizers is applied to the plot. So, we state the explanatory variable as "type of fertilizer."

Incorrect. Try again.

2

Incorrect. the response variable is the outcome measured on each individual. In this example, the individual is the plot. On each plot, the corn yield was measured. So, the response variable is "corn yield."

Correct. the response variable is the outcome measured on each individual. In this example, the individual is the plot. On each plot, the corn yield was measured. So, the response variable is "corn yield."

Incorrect. Try again.

2

Incorrect. Since all plots received fertilizer, there is no control in this study.

Correct. Since all plots received fertilizer, there is no control in this study.

Incorrect. Try again.

2

Incorrect. With no control, there is no need for a placebo - only use a placebo with people or animals.

Correct. With no control, there is no need for a placebo - only use a placebo with people or animals.

Incorrect. Try again.

2

Incorrect. The subject is an individual upon whom a treatment is applied. In this study, a treatment was given to a student. "A student with polio" categorizes with respect to the response variable and "A student who received the vaccine" categorizes with respect to the explanatory variable. We don't do that when stating the subject.

Correct. The subject is an individual upon whom a treatment is applied. In this study, a treatment was given to a student. "A student with polio" categorizes with respect to the response variable and "A student who received the vaccine" categorizes with respect to the explanatory variable. We don't do that when stating the subject.

Incorrect. Try again.

2

Incorrect. The explanatory variable must describe all possible treatments. This study has two treatments: vaccine and a placebo or saline solution. So, "content of injection" is a correct statement of the explanatory variable. "Vaccine against polio" gives only one on the two possible treatments so it is not a correct statement of the explanatory variable.

Correct. The explanatory variable must describe all possible treatments. This study has two treatments: vaccine and a placebo or saline solution. So, "content of injection" is a correct statement of the explanatory variable. "Vaccine against polio" gives only one on the two possible treatments so it is not a correct statement of the explanatory variable.

Incorrect. Try again.

2

Incorrect. At the end of the study, each student is examined to determine whether he/she contracts polio. "Percent of students who contract polio" is an aggregate measure, not a measure on an individual. The response variable is a measure on an individual.

Correct. At the end of the study, each student is examined to determine whether he/she contracts polio. "Percent of students who contract polio" is an aggregate measure, not a measure on an individual. The response variable is a measure on an individual.

Incorrect. Try again.

2

Incorrect. The control group is the group of individuals NOT receiving the active treatment. In this study, the students receiving saline injections did not receive the active treatment and constitute the control group.

Correct. The control group is the group of individuals NOT receiving the active treatment. In this study, the students receiving saline injections did not receive the active treatment and constitute the control group.

Incorrect. Try again.

2

Incorrect. The placebo or "fake" treatment is the saline injection.

Correct. The placebo or "fake" treatment is the saline injection.

Incorrect. Try again.

2

Incorrect. "Content of injection" can be either saline solution or vaccine, so it is categorical.

Correct. "Content of injection" can be either saline solution or vaccine, so it is categorical.

Incorrect. Try again.

2

Incorrect. "whether individual contracted polio" can be either yes or no, so it is categorical.

Correct. "whether individual contracted polio" can be either yes or no, so it is categorical.

Incorrect. Try again.

2

Incorrect. The question basically gives the definition of "confounding."

Correct. The question basically gives the definition of "confounding."

Incorrect. Try again.

2

Incorrect. The question basically gives the definition of "interaction."

Correct. The question basically gives the definition of "interaction."

Incorrect. Try again.

2

Incorrect. The question basically gives the definition of "lurking variable."

Correct. The question basically gives the definition of "lurking variable."

Incorrect. Try again.

2

Incorrect. A lurking variable is one not studied, but which affects the relationship between the explanatory variable (type of patch) and the response variable (whether subject quit smoking).

Correct. A lurking variable is one not studied, but which affects the relationship between the explanatory variable (type of patch) and the response variable (whether subject quit smoking).

Incorrect. Try again.

2

Incorrect. In proposal B, all clothes washed with the name brand detergent were also washed in hot water; all clothes washed with the store brand were washed in cold water.

Correct. In proposal B, all clothes washed with the name brand detergent were also washed in hot water; all clothes washed with the store brand were washed in cold water.

Incorrect. Try again.

2

Incorrect. In proposal B, Mr. Smith taught using multi-media and Mr. Williams taught using overheads; we can't tell whether differences in test scores are due to type of teaching or due to teacher.

Correct. In proposal B, Mr. Smith taught using multi-media and Mr. Williams taught using overheads; we can't tell whether differences in test scores are due to type of teaching or due to teacher.

Incorrect. Try again.

2