Observational Studies and Experiments

Question 1

To increase attendance for a flower show, flower shops in the area offered discount coupons to their customers. Show attendance was higher this year, which the organizers attributed to the many discount coupons attendees used. However, the organizers are warned that weather could be a confounding variable in interpreting the rise in attendance.

Revolt · Accepted Answer

D: Because the weather was generally better this year compared to last year, the attendance may have increased.

Question 2

Two methods are proposed to measure the effectiveness of a brand of sunscreen.Method A: Survey adults visiting a beach on a busy weekend. Ask each adult which brand of sunscreen they are using, and assess their arms for sun exposure.Method B: Volunteers are randomly assigned to one of two brands of sunscreen. Each volunteer is asked to report back at the end of the day, and their arms are assessed for sun exposure.

Revolt · Accepted Answer

D: Method B is an experiment because it randomly assigns volunteers a sunscreen, while method A is an observational study.

Question 3

To increase attendance for a flower show, the organizers have chosen flower shops in the area to offer discount coupons to their customers. Half of the stores receive discount coupons for admission, while the other half of the stores receive two-for-one admission coupons. The organizers then compare the number of each type of coupon redeemed at the show.

Revolt · Accepted Answer

C: The explanatory variable is the type of coupon. The response variable is number of number of coupons redeemed.

Question 4

An article in a psychology journal claims that young students who play a musical instrument tend to have higher test scores on state math exams.

Revolt · Accepted Answer

D: Students who play a musical instrument tend to excel in other skills, which may explain their higher math scores.

Question 5

A clothing company is considering a new insulation for winter coats. To collect customer satisfaction data on the new insulation, the company is considering two methods.Method 1: The company offers the first 50 employees who volunteer to try out a coat with new insulation if they will report their satisfaction level after one month. At the end of the month, the 50 volunteers describe their satisfaction with the coat's performance.Method 2: The company takes 50 volunteers and randomly assigns 25 of them to coats with the new insulation and the other 25 to coats with the current insulation. All volunteers wear the coats for a month and then describe their satisfaction with the coats’ performance.

Revolt · Accepted Answer

C: Method 2 is an experiment because volunteers are assigned one of the two insulation types.

Question 6

A farmer would like to determine if a new liquid fertilizer is an improvement compared with the fertilizer currently used. To collect data, two methods are considered.Method 1: Visit a local farm currently using the new liquid fertilizer and measure the heights of plants grown at the farm.Method 2: Choose a plot of land and divide it into 16 smaller plots. Randomly select 8 of the plots to use the new fertilizer and 8 of the plots to use the current fertilizer. Measure and compare plant heights in the 16 plots.

Revolt · Accepted Answer

D: Method 2 is an experiment because the plots are randomly assigned a fertilizer.

Question 7

A home-improvement store offers a new brand of lawn food that claims to reduce the number of weeds by 30% over a different brand of lawn food. To test the claim, a homeowner plans to use the new brand of lawn food on half of his lawn and the original brand on the other half. The homeowner will count the number of weeds that appear after a month on each half of the lawn. A neighbor explains that there may be confounding variables, such as shade, that might also explain the relationship.

Revolt · Accepted Answer

D: The parts of the lawn that receive the new lawn food may also get more shade than other parts of the lawn, and the shade might also cause fewer weeds.

Question 8

Many golfers wear wrist bracelets containing magnets because they claim the magnets improve balance and the length of shots played off the tee. A golfer would like to determine if the claim has merit and plans to collect data on the length of shots played by golfers who use the magnetic bracelets. Another golfer points out that many golfers who purchase the bracelets also purchase other expensive golf equipment, such as golf clubs, and this could be a confounding variable.

Revolt · Accepted Answer

D: Because golfers may use both magnetic bracelets and expensive golf clubs, it will be difficult to determine which variable contributes most to longer shots.

Question 9

An auto-parts store offers a fuel additive that claims to increase a vehicle’s gas mileage. The additive is poured into a vehicle’s gasoline tank after the tank is filled. To measure the claim, the store offers a free bottle of the additive to customers who drive SUV's, who then provide information about their gas mileage on the store website. A customer argues that the type of vehicle could be a confounding variable in this study.

Revolt · Accepted Answer

D: Because vehicles of different sizes may respond differently to the additive, it may be difficult to conclude whether the additive improves gas mileage for all vehicles.

Question 10

Many golfers wear wrist bracelets containing magnets because they claim the magnets improve balance and the length of shots played off the tee. A golfer would like to determine if the claim has merit and proposes two methods for collecting data.Method 1: As golfers approach the first tee, give some golfers wrist bracelets with magnets and some golfers wrist bracelets without magnets. During the round of golf, keep track of the length of the golfers’ shots.Method 2: Contact golfers who have purchased wrist bracelets with magnets and ask them to provide information about their shot length.

Revolt · Accepted Answer

B: Method 2 is an observational study because it does not attempt to influence responses.

Observational Studies and Experiments Answers

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