StatTutor Lesson - Subjects, Factors, Treatments

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StatTutor: Subjects, Factors, Treatments
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      Questions 1-3

      70

      Question 1.

      Upon what is a treatment applied?

      A.
      B.
      C.

      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

      Questions 4-6

      108

      Question 4.

      True or false: A control is any treatment without the active ingredient.

      A.
      B.

      Incorrect. This is a correct statement.
      Correct. This is a correct statement.
      Incorrect. Try again.
      2

      Question 7

      135

      Question 7.

      For this study, what is the individual upon which the treatments are applied?

      A.
      B.
      C.
      D.

      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

      Question 8

      141

      Question 8.

      What are the treatments?

      A.
      B.
      C.
      D.

      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

      Question 9

      148

      Question 9.

      What is the explanatory variable?

      A.
      B.
      C.
      D.

      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

      Question 10

      159

      Question 10.

      What is the response variable? i.e., what is measured on each plot?

      A.
      B.
      C.
      D.

      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

      Question 11

      169

      Question 11.

      Was a control used in this experiment?

      A.
      B.

      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

      Question 12

      178

      Question 12.

      Was a placebo administered in this study?

      A.
      B.

      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

      Question 13

      309

      Question 13.

      What is the subject?

      A.
      B.
      C.
      D.

      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

      Question 14

      316

      Question 14.

      What is the explanatory variable?

      A.
      B.
      C.
      D.
      E.

      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

      Question 15

      348

      Question 15.

      What is the response variable?

      A.
      B.
      C.
      D.
      E.

      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

      Question 16

      364

      Question 16.

      What is the control group?

      A.
      B.
      C.
      D.

      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

      Question 17

      371

      Question 17.

      What is the placebo?

      A.
      B.
      C.
      D.

      Incorrect. The placebo or "fake" treatment is the saline injection.
      Correct. The placebo or "fake" treatment is the saline injection.
      Incorrect. Try again.
      2

      Questions 18-19

      439

      Question 18.

      What type of variable is the explanatory variable, "content of injection?"

      A.
      B.

      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

      Questions 20-22

      498

      Question 20.

      Which of the following involves two variables whose effects on the response variable cannot be separated?

      A.
      B.
      C.

      Incorrect. The question basically gives the definition of "confounding."
      Correct. The question basically gives the definition of "confounding."
      Incorrect. Try again.
      2

      Question 23

      627

      Question 23.

      Why is "presence or absence of other smokers in the home" a lurking variable?

      A.
      B.

      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

      Question 24

      679

      Question 24.

      Which proposal has confounding?

      A.
      B.

      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

      Question 25

      835

      Question 25.

      Which proposal has confounding?

      A.
      B.

      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