Question

select all the correct answers.

a manufacturer claims that its new hand sanitizer reduces the number of days an average person is sick in a year. to test this claim, a researcher decided to conduct an experiment. the researcher randomly selected 300 people, divided into subject groups by age. over the course of a year, all the subjects regularly used the hand sanitizer. at the end of the year, the researcher compared the number of days that the subjects in each group were sick.

which statements about this experiment are true?

• this study uses a control group.
• this study uses blocking.
• this study uses blinding.
• this study uses random sampling.
• this study uses a repeated measures design.

Explanation:

Analyze experimental design components

• Control group: The text states "all the subjects regularly used the hand sanitizer." There is no untreated group or placebo group for comparison, so there is no control group.
• Blocking: The researcher "divided [subjects] into subject groups by age" before comparing results. Dividing subjects into homogeneous groups based on an attribute (age) that might affect the outcome is blocking.
• Blinding: There is no mention of subjects or researchers being unaware of who received what treatment (especially since everyone used the sanitizer).
• Random sampling: The researcher "randomly selected 300 people" from the population, which constitutes random sampling.
• Repeated measures: Subjects were not measured multiple times under different treatment conditions; they were only measured once at the end of the year.

Evaluate statements

• "This study uses a control group" is False.
• "This study uses blocking" is True.
• "This study uses blinding" is False.
• "This study uses random sampling" is True.
• "This study uses a repeated measures design" is False.

Answer:

• This study uses a control group.
• This study uses blocking. (Correct answer)
• This study uses blinding.
• This study uses random sampling. (Correct answer)
• This study uses a repeated measures design.