Experiments and Observational Studies

Which of the following is not a principle of experimentation?

• Randomly allocating experimental units to treatments
• Stratifying the experimental units into groups of similar indiviudals and applying a different treatment to each strata
• Replicating to measure overall experimental error and increase precision
• Using a control group to determine whether a treatment really works

The advantage of experiments over observational studies is that

• experiments can be used to establish causation.
• experiments do not have biased results because of the control group.
• the variables in an experiment cannot be confounded.
• the principle of blocking is applicable in experiments but not in surveys.

Tags

CCSS.HSS.IC.B.3

CCSS.HSS.IC.B.5

For which of the following purposes would it be most unreasonable to use a census?

• to determine the proportion of students with a learning disability in a small rural area high school
• to determine the proportion of red snappers with a high mercury level in the Gulf of Mexico
• to determine the mean wage earned by construction workers in a small town
• to determine the mean selling price of houses in your neighborhood

Two variables in a study are said to be confounded if

• one cannot separate their effects on a response variable.
• they are highly correlated.
• they do not have a normal distribution.
• one of them is a placebo.

In order to investigate whether women are more likely than men to prefer Democratic candidates, a political scientist selects a large sample of registered voters, both men and women. She asks every voter whether they voted for the Republican or the Democratic candidate in the last election. This is

• a simple random sample
• a block design
• a double-blind experiment
• an observational study

Which of the following distinguishes an observational study from a randomized experiment?

• In an observational study volunteers are always used, whereas in a randomized experiment a random sample is always taken from the population.
• In an observational study a random sample is always taken from the population, whereas in a randomized experiment volunteers are always used.
• In an observational study treatments are not randomly assigned, whereas in a randomized experiment treatments are always randomly assigned.
• In an observational study a control group is never used, whereas in a randomized experiment a control group is always used.

In what experiment are neither the subject nor those who interact with them and measure the response variable ?

• Double Blind

• Statistaclly significant

Your statistics class has 30 students. You want to call an SRS of 5 students from your class to ask where they use a computer for the online quizzes. You label the student 01, 02, ..., 30. You enter the table of random digits at this line:

14459 26056 31424 80371 65103 62253 22490 61181

Your SRS contains the students listed:

• 14,45,92,60,56

• 14,31,03,10,22

• 14,03,10,22,22

• 14,03,10,22,06

• 14,03,10,22,11

A gardener wants to try different combinations of fertilizer (none, 1 cup, 2 cups) and mulch (none, wood chips, pine needles, plastic) to determine which combination produces the highest yield for a variety of green beans. He has 60 green bean plants to use in the experiment. If he wants an equal number of plants to be assigned to each treatment, how many plants will be assigned to each treatment?

• 1

• 3

• 4

• 5

• 12

Tags

CCSS.5.NBT.B.6

CCSS.5.NF.B.3

Principal Rusk picks 75 students at a recent varsity football game to be used for the sample.  This is what type of sampling design?

• SRS
• Stratified
• Convenience
• Voluntary Response

Tags

CCSS.HSS.IC.B.3