Chapter 5 and 6 practice

Students in a large statistics class were randomly divided into two groups. The first group took the midterm exam with soft music playing in the background while the second group took the exam with no music playing. The scores of the two groups on the exam were compared. In this experiment, the response variable is A. the score on the midterm exam. B. whether or not music was playing during the exam. C. the placebo. D. a lurking variable.

A. the score on the midterm exam.

If you were testing treatments A, B and a control (Treatment C) for their effectiveness in shortening the time it takes a wound to heal, what might be a good blocking variable? A.) Age. B.) Income. C.) Hair color. D.) Eye color.

A.) Age.

At USC, there are currently STAT 110 classes with 50 and 200 students. The statistics Department wants to know if class size affects student performance. At the end of the semester, they compare Final Exam scores from the class of size 50 to the Final Exam scores from the class of size 200. What is the explanatory variable? A.) Class size. B.) 50 or 200 students. C.) Final Exam score. D.) STAT 110 students. E.) The teacher.

A.) Class size.

Students in a large statistics class were randomly divided into two groups. The first group took the midterm exam with soft music playing in the background while the second group took the exam with no music playing. The scores of the two groups on the exam were compared. How would you best describe the design of this experiment? A.) Completely Randomized B.) Matched Pair C.) Blocked D.) Simple Random Sample

A.) Completely Randomized

Confounding often defeats attempts to show that one variable causes changes in another variable. Confounding means that the effects of several variables are mixed up, so we cannot say which is causing the response. A.) True. B.) False.

A.) True

Three essential features of all statistically designed experiments are (check the three correct answers below) A.) compare treatments. B.) use the double-blind method. C.) use large samples. D.) always have a placebo group. E.) use chance to assign subjects to treatments. F.) use a block design.

A.) compare treatments C.) use large samples E.) use chance to assign subjects to treatments

Medical experiments, such as one to compare aspirin with a placebo for preventing heart attacks, are often double-blind. This means that A.) neither the subject nor the doctor knows which treatment the subject received. B.) the subjects choose which treatment they get, but do not tell the doctor. C.) the doctor chooses which treatment to give the subject, but does not tell the subject. D.) the subjects are not told either their treatment or their medical condition. E.) all individual data are kept confidential.

A.) neither the subject nor the doctor knows which treatment the subject received.

An important reason for the use of randomization in designing experiments is that it tends to A.) reduce the effect of confounding/lurking variables. B.) allow double-blinding. C.) eliminate response error. D.) reduce the placebo effect.

A.) reduce the effect of confounding/lurking variables.

Students in a large statistics class were randomly divided into two groups. The first group took the midterm exam with soft music playing in the background while the second group took the exam with no music playing. The scores of the two groups on the exam were compared. In this experiment, the explanatory variable is: A. the score on the midterm exam. B. whether or not music was playing during the exam. C. the placebo. D. a lurking variable.

B. whether or not music was playing during the exam.

At USC, there are currently STAT 110 classes with 50 and 200 students. The statistics Department wants to know if class size affects student performance. At the end of the semester, they compare Final Exam scores from the class of size 50 to the Final Exam scores from the class of size 200. What are the treatments? A.) Class size. B.) 50 or 200 students. C.) Final Exam score. D.) STAT 110 students. E.) The teacher.

B.) 50 or 200 students.

At USC, there are currently STAT 110 classes with 50 and 200 students. The statistics Department wants to know if class size affects student performance. At the end of the semester, they compare Final Exam scores from the class of size 50 to the Final Exam scores from the class of size 200. What is the response variable? A.) Class size. B.) 50 or 200 students. C.) Final Exam score. D.) STAT 110 students. E.) The teacher.

C.) Final Exam score.

Hearing loss is more common among premature infants than among full-tem infants. This was thought to be an effect of premature birth. It has recently been suggested that hearing loss may be caused by the high noise level of the incubators in which the premature infants are placed. This is an example of: A.) statistical significance. B.) a designed experiment. C.) confounding between two variables. D.) a matched pair design.

C.) confounding between two variables.

An experiment compares two brands of automobile tires. Each of a number of cars is equipped with one tire of each brand on a rear wheel (the order is randomized from car to car) and tread wear is measured periodically. This is called a: A.) simple random sample. B.) completely randomized design. C.) matched pairs design. D.) double-blind design.

C.) matched pairs design.

At USC, there are currently STAT 110 classes with 50 and 200 students. The statistics Department wants to know if class size affects student performance. At the end of the semester, they compare Final Exam scores from the class of size 50 to the Final Exam scores from the class of size 200. Who/What are the subjects? A.) Class size. B.) 50 or 200 students. C.) Final Exam score. D.) STAT 110 students. E.) The teacher.

D.) STAT 110 students.

In a randomized block design, the blocks often represent levels of: A.) the explanatory variable. B.) the response variable. C.) placebo dosage. D.) a variable suspected of being confounded with the explanatory variable.

D.) a variable suspected of being confounded with the explanatory variable.