PBS - 4.2 Experimental Design

If I water the plant more often, then it will grow taller. Name the explanatory variable.

• The height of the plant

• The size of the pot

• The amount of water

• The amount of light.

If I water the plant more often, then it will grow taller. Name the response variable.

• The amount of water.

• The amount of soil.

• The height of the plant.

• The amount of water.

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 six times, three times while wearing a floral-scented mask and three times wearing an unscented mask. The three trials for each mask closely followed one another. Testers measured 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 than those wearing the unscented mask, although the difference was not statistically significant. This study is

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

An amateur gardener decides to change varieties of tomatoes for this year to see if the yield is improved. He puts 6 of the old type of tomato plants and 6 of the new tomato plants in his garden. The average yield for the old plants was 11.3 pounds and the average for the new plants was 14.5 pounds. This is an example of

• an experiment
• an observational study

In order to assess the effects of exercise on reducing cholesterol, a researcher sampled 50 people from a local gym who exercised regularly and 50 people from the surrounding community who did not exercise regularly. They each reported to a clinic to have their cholesterol measured. The subjects were unaware of the purpose of the study, and the technician measuring the cholesterol was not aware of whether subjects exercised regularly or not. This is

• an observational study
• an experiment

210 college students were randomly assigned to play either a violent or nonviolent video game.  A short time later, the students were presented with the opportunity to trivially harm another person and results comparing the two groups were recorded.
Is this study OBSERVATIONAL or EXPERIMENTAL? 

• Observational
• Experimental

Tags

CCSS.HSS.IC.B.3

CCSS.HSS.IC.B.5

A study is conducted to investigate the relationship between owning pets and happiness. 100 subjects are randomly selected and data on whether or not a pet is owned and a happiness score (1‐10, 10 being extremely happy) are obtained.
Is this an OBSERVATIONAL or EXPERIMENTAL study?

• Observational
• Experimental

Tags

CCSS.HSS.IC.B.3

Which of the following is most useful in establishing cause-and-effect relationships?

• A complete census
• A least squares regression line showing high correlation
• A simple random sample (SRS)
• A well-designed, well-conducted observational study incorporating chance
• A controlled experiment

Tags

CCSS.HSS.IC.B.3

Does "an apple a day keep the doctor away?" A study is proposed to pick a random sample of 100 healthy adults, divide them into two groups based on who eats apples regularly and who doesn't, follow them for 5 years, and calulate the mean number of doctor visits of each group. Which of the following is correct?

• This is an observational study because no treatment is applied.
• This is an experiment, but one design fault is that the two groups might be different sizes.
• This is an experiment where eating apples is the treatment but there is no control.
• This is an experiment, but no causation can be concluded because there was no random assignment.
• This is an experiment, but no causation can be concluded because of confounding variables.

Tags

CCSS.HSS.IC.B.3

Before playing a soccer game, players rested for 2, 4, or 6 hours. Half of each group was given an energy drink before starting the game. Determine the number of factors, levels for each factor, and number of treatments.

• 1 factor with 2 levels; 5 treatments
• 2 factors, one with 1 level and one with 2 levels; 3 treatments
• 2 factors, one with 2 levels and one with 3 levels; 5 treatments
• 2 factors, one with 2 levels and one with 3 levels; 6 treatments
• 3 factors, each with 2 levels; 6 treatments

Tags

CCSS.HSS.IC.B.3