Experimental Design

One group of subjects was given an herbal supplement and another group was given a placebo. After one year, the number of illnesses each group had was compared.

• Observational Study

• Experiment

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CCSS.HSS.IC.B.3

Four groups of randomly selected people are assigned a different diet. After six months, the blood pressures of each group are compared.

• Observational Study

• Experiment

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CCSS.HSS.IC.B.3

To test the effects of breakfast on grades I ask my students if they ate breakfast and then compare the breakfast eaters grades to the non-breakfast eaters.

This is an example of:

• Observational study

• Experiment

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CCSS.HSS.IC.B.3

An advertising agency is testing the effectiveness of a new commercial. They are trying out the commercial in three different time lengths (15, 30, and 60 seconds) and two formats (animated vs. live action). Each test audience will rate the product after seeing the commercial shown in one way. Which description is correct?

• An experiment with 2 factors (length and format), one having 3 levels (15, 30, 60) and the other having 2 levels (animated and live) for 6 treatments.

• An experiment with 2 factors (length and format) at 5 levels (15, 30, 60, animated and live) for 5 treatments.

• An experiment with 1 factor (length) blocked by format with 3 levels (15, 30, 60).

• A sample survey with two questions and one response.

• A sample stratified by length and format.

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CCSS.HSS.IC.B.3

You want to see if students who have a 4.0 grade point average study more than those who do not.

• experiment

• observational study

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CCSS.HSS.IC.B.3

You want to compare the health of students who walk to school to the health of students who ride the bus

• experiment

• observational study

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CCSS.HSS.IC.B.3

Why is the placebo effect used?

• To compare results between the real medicine and placebo

• To make new medicine

• To train doctors

• To make food

Runners after an ultramarathon commonly develop respiratory infections. We want to know if taking 600 milligrams of vitamin C daily will reduce these infections. Researchers randomly assigned 100 ultramarathon runners to receive either vitamin C or placebo. All subjects were watched for 14 days after the big race to see if infections developed. What are the possible lurking variables?

• Age of the runner
• weight of the runner
• gender of the runner
• all of the above

Tags

CCSS.HSS.IC.B.3

Runners after an ultramarathon commonly develop respiratory infections. We want to know if taking 600 milligrams of vitamin C daily will reduce these infections. Researchers randomly assigned 100 ultramarathon runners to receive either vitamin C or placebo. All subjects were watched for 14 days after the big race to see if infections developed. The type of design used here?

• matched pairs
• randomized block
• completely randomized
• stratified 

Tags

CCSS.HSS.IC.B.3

Can pleasant aromas help a student learn better? Two researchers believed that the presence of a floral scent could improve a person's learning ability in certain situations. They had 22 people work through a pencil-and-paper maze 6 times. Three of the times they wore a floral-scented mask and three times they wore an unscented mask. The three trials for each mask followed one another. Testers measures the length of time it took subjects to complete each of the six trials. They reported that, on average, subjects wearing the floral-scented mask completed the maze more quickly that those wearing the unscented mask, although, the difference was not statistically significant. This study is:

• a convenience sample
• an oberservational study
• an experiment, but not double-blind
• a double-blind experiment

Tags

CCSS.HSS.IC.B.3