Answers NC-Math 4 CRObservational Studies and Experiments

How to Experiment Well Answers

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A researcher is comparing three new formulas for grass killer. To conduct the experiment, the researcher purchases 30 pieces of sod from various vendors to use in the study. The 30 pieces of sod are laid out in three different areas. The researcher places three slips of paper in a bowl labeled formula 1, formula 2, and formula 3 and randomly picks a piece of paper to apply that formula to the sod in the first area. Then the researcher picks again and applies that formula to the second area. Finally, the last formula is used on the last area.

The researcher should not have laid out the pieces of sod in different areas.

The researcher did not randomly assign the pieces of sod to the treatment groups.

The researcher did not randomly pick the vendors when purchasing the pieces of sod.

The researcher did not use randomization when selecting the pieces of sod from the vendors.

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Aeronautical researchers have developed three different processes to pack a parachute. They want to compare the different processes in terms of time to deploy and reliability. There are 5,100 objects that they can drop with a parachute from a plane. Using a table of random digits, the researchers will randomly place the items, labeled 0001–5100, into three equally sized treatment groups suitable for comparison. Carry out the random assignment using the given selection from a table of random digits, starting with the first row and first column.

2719, 2825, 3031, 2628, 3562

6011, 8572, 2719, 5769, 2825

2719, 2825, 3031, 2628, 2719

601, 18, 57, 227, 1957

An education researcher is interested in comparing the learning outcomes of students who are taught a lesson using five different teaching techniques. Using a table of random digits, the researcher needs to randomly place 75 students, labeled 01–75, into five equally sized treatment groups suitable for comparison. Carry out the random assignment using the given section from a table of random digits, starting with the first row and first column.

8, 7, 2, 6, 5, 4, 1

26, 54, 72, 19, 70, 62, 30

26, 54, 72, 26, 19, 70, 62

87, 26, 54, 00, 88, 77, 72

A researcher is comparing three new formulas for grass killer. To conduct the experiment, the researcher purchases 30 pieces of sod from a local vendor and selects the treatment groups by placing slips of paper numbered 1–30 in a hat. To make three groups for the three formulas, the researcher randomly selects 10 numbers, making sure to mix the slips between each selection, to get the formula 1 group. Then the researcher selects 10 more numbers to get the formula 2 group. The remaining 10 numbers make up the formula 3 group.

The researcher did not randomly pick the vendor.

The researcher did not randomly pick the 30 pieces of sod.

The researcher did not assign a treatment to each group of sod.

The researcher did not label the pieces of sod before randomly selecting them.

A researcher wants to know if eating a mint affects whether people can distinguish between two popular orange juice brands. To conduct an experiment, the researcher places participants in two groups. The treatment group will eat a mint before drinking a juice, while the control group will not eat a mint before drinking. Then the participants will guess the juice brand.

that there will be the same number of participants in both groups.

that the experiment results can be generalized to all people.

that both groups have participants that like both popular juice brands.

that both groups are roughly equivalent with regards to demographics and juice preferences.

A researcher wants to know if eating a mint affects whether people can distinguish between two popular orange juice brands. To conduct an experiment, the researcher places 50 participants in two groups. The treatment group will eat a mint before drinking a juice, while the control group will not eat a mint before drinking. Then the participants will guess the juice brand. To select the groups, the researcher labels each participant with a number and selects slips of paper labeled 1–50 from a bowl at random. The first 25 participants whose numbers are selected will be the treatment group, while the other 25 will be the control group.

should be roughly equivalent because both groups will have 25 participants.

should be roughly equivalent because the participants were labeled and then randomly selected for the groups.

might not be roughly equivalent because one group may contain people that drink more juice than the other group.

might not be roughly equivalent because one group may contain more people that prefer a particular juice brand.

A teacher wants to know if burning a scented candle affects students’ performance on pop quizzes. In the experiment, there will be a treatment group and a control group each taking their quizzes in a room that either does or does not have a scented candle burning. On a randomly chosen day, the first 15 students who arrive to class will be the control group while the last 15 students who arrive will be the treatment group.

The characteristics of the two groups should be roughly equivalent because both groups have 15 students.

The characteristics of the two groups should be roughly equivalent because the students were split into groups on a randomly chosen day.

The characteristics of the two groups might not be roughly equivalent because the students were not labeled and given a random number to place them in one of the groups.

The characteristics of the two groups might not be roughly equivalent because students who arrive around the same time might be friends and have similar preferences for scented candles.

A researcher is interested in whether using mental imagery can help people remember specific details when given information. To conduct the experiment, the researcher asks 100 volunteers to participate. The researcher places everyone’s name in a hat and randomly selects 50 names, making sure to sure to mix the names between each selection.

The researcher did not use enough randomization in the process.

The researcher used volunteers instead of randomly selected people from the population.

The researcher did not assign the 50 names to the treatment group or the control group.

The researcher should have used numbers instead of names for confidentiality reasons.

Aeronautical researchers have developed three different processes to pack a parachute. They want to compare the different processes in terms of time to deploy and reliability. There are 1,200 objects that they can drop with a parachute from a plane. Using a table of random digits, the researchers will randomly place the 1,200 items into three equally sized treatment groups suitable for comparison.

1–3

1–1200

0000–1200

0000–1199

A researcher is interested in whether using mental imagery can help people remember specific details when given information. To conduct the experiment, the researcher asks 100 volunteers to participate. The first 50 people to arrive are put in the treatment group, while the rest are put in the control group. The volunteers’ names are written on slips of paper and placed in a hat. The researcher randomly selects a name to determine whose turn it is to participate.

The researcher did not use randomization to assign people to the treatment group or the control group.

The researcher did not properly label the slips of paper before putting them into the hat.

The researcher used volunteers instead of randomly selected people from the population.

The researcher did not allow all participants the same chance to be included in the treatment group.

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