Unit 3 Review - Sampling and Experimental Design

Why do we use control groups in experiments?

• To eliminate confounding variables

• To control the subjects to make sure everyone participates equally

• To control how the experiment is conducted and make sure that the results are what we expect

• To ensure that randomized assignment is achieved

• To reduce the variability in the response variable between the two groups so that any difference is due to the treatment alone

To gather baseline data for a new standardized test for 8th grade students in the state of Wisconsin, a random sample of 15 middle schools were selected. The new test was administered to every 8th grade student in the selected schools. What kind of sample is this?

• A simple random sample

• A stratified random sample

• A cluster sample

• A systematic random sample

• A voluntary response sample

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CCSS.HSS.IC.B.3

Suppose that 35% of the registered voters in a state are registered as Republicans, 40% as Democrats, and 25% as Independents. A newspaper wants to select a sample of 1000 registered voters to predict the outcome of the next election. If they randomly selected 350 Republicans, randomly selected 400 Democrats, and randomly selected 250 Independents, did this sampling procedure result in a simple random sample of registered voters from this district?

• Yes, because each registered voter had the same chance of being chosen.

• Yes, because random chance was involved.

• No, because not all registered voters had the same chance of being chosen.

• No, because there were a different number of registered voters from each party.

• No, because not all possible groups of 1000 registered voters had the same chance of being chosen.

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Dave is an avid gardener and has a self-proclaimed "green thumb". He wants to increase the yield of his habanero pepper plants and wishes to test four different combinations of fertilizer (none, Fertilizer A, Fertilizer B, and both) also with three different types of soil (sand, silt, and clay). How many different treatment groups will Dave have in his experiment?

• 3

• 4

• 7

• 12

• 64

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CCSS.HSS.IC.B.3

Researchers wish to design a matched pairs experiment to determine the effects of a medication on reducing LDL cholesterol levels in 400 adults in the 65 and older age group who have elevated levels of LDL. Which of the following represents such a design?

• They compare the cholesterol levels of each patient before he/she begins a daily regimen of the medicine to the patient’s cholesterol level after six weeks of using the medication.

• They compare the cholesterol levels of the 400 patients using the medicine for six weeks with the cholesterol levels of 400 other adults who are 65 and older who exhibited elevated cholesterol levels and did not take the medicine.

• They compare the mean cholesterol level of the 400 patients six weeks after using the medicine with a published national mean cholesterol level for all adults who are 65 and older.

• They compare the cholesterol levels of the 400 patients using the medicine for six weeks with the cholesterol levels of 400 adults in the 65 and older age group who were taking a placebo.

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CCSS.HSS.IC.B.3

Proactive has developed a new treatment for acne. You think the age of the participant might influence their reaction to the new treatment, so you separate them into two groups: one group of 18 – 25 year olds and one group of 26 and older year olds. Within the group, half of them are given the new treatment, and the other half are given a placebo treatment. The basic design of this study is

• completely randomized

• blocked by age group

• completely randomized, blocked by age group

• randomized, blocked by age group and type of medication

• a matched pairs design

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CCSS.HSS.IC.B.3

As an environmentalist, Diana is appalled at the recent report that states the chemical factory in her town has no influence on the quality of river life. She strongly objects and creates an experiment to measure the oxygen level at various points along the river, suspecting that the chemical plant decreases the oxygen level in the river, causing wildlife disruption. She takes sites 100, 200, and 300 meters along the river, down from the plant. At each site, she measures the surface oxygen level, the oxygen level at mid-depth, and the oxygen level at the bottom of the river. What type of study was conducted, and what is the response variable of the study?

• An experiment was conducted, and the response variable is the oxygen level.

• An experiment was conducted, and the response variable is the depth of the water.

• An experiment was conducted, and the response variable is the three different site locations.

• An observational study was conducted, and the response variable is the oxygen level.

• An observational study was conducted, and the response variable is the depth of the water.

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CCSS.HSS.IC.B.3

Your football coach finds a new exercise program that will increase upper-body strength better than lifting weights. He wants to start this new program in the off season with the team. He lets his players choose which of the two treatments they will undergo for 3 weeks – exercise or weight lifting. He will use the number of push-ups a player can do at the end of the experiment as the response variable. Which principle of experimental design does his plan violate?

• Randomization

• Control

• Replication

• Comparison

• Blocking

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CCSS.HSS.IC.B.3

The booster club needs volunteers to sign up to work the concession stand for home games. They have a low participation rate, so they want to see if a new incentive would help. They randomly select 50 numbers from a list of all parents of the student athletes. From the 50 numbers they called, 8 of them picked up and 6 of them said that they would volunteer with an incentive. What is the correct conclusion that can be drawn?

• We can conclude that 75% of athlete parents would volunteer at the concession stand if there was an incentive.

• We can conclude that 12% of athlete parents would volunteer at the concession stand if there was an incentive.

• No conclusion can be drawn because this survey suffers from nonresponse bias.

• No conclusion can be drawn because this survey suffers from voluntary response bias.

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CCSS.7.SP.A.2

A psychologist plans a study to determine if high school students read faster with their right eye or left eye alone. Fifty high school students are randomly selected for the study. Which of the following correctly describes a matched pairs design?

• Label each student 1 – 50 and use a random number generator (ignoring repeats), and choose 25 numbers. Those students assigned to those 25 numbers will be part of the treatment that reads with their right eye. The rest of the students will be assigned to read with their left eye.

• Each student will read with each eye, one at a time. To decide which eye they will read with first, a coin will be flipped for each student. If the coin is heads, the student will read with their right eye first and their left eye second. If the coin is tails, the student will read with their left eye first and their right eye second.

• Split the 50 students up into males and females. Then, within each gender group, randomly assign half of the subjects to read with their right eye and half the subjects to read with their left eye.

• Split the 50 students up into males and females. To decide which group will read with each eye, a coin will be flipped. If the coin is heads, the males will read with their left eye and the females will read with their right eye. If the coin is tails, the males will read with their right eye and the females will read with their left eye.

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