In an observational study, confounding means
a. having more than one response variable.
b. that the effect of the explanatory variable on the response variable changes for different categories of a third variable.
c. that the effects of several variables are tested at one time.
d. that the effect of the explanatory variable on the response variable can't be separated from the effect of other variables on the response.
Q. 2A researcher conducts a study to determine whether or not taking Vitamin C prevents colds. What is the explanatory variable in this study?
a. Whether or not one takes Vitamin C.
b. Whether or not one gets colds.
c. Whether or not one is a participant in the study.
d. Whether or not one knows which treatment one is taking.
Q. 3A researcher asked random samples of 50 kindergarten teachers and 50 12th grade teachers how much of their own money they spent on school supplies in the previous school year. They wanted to see if teachers at one grade level spend more than teachers at the other grade level. In this study, it turns out that 12th grade teachers generally earn more money than kindergarten teachers. The variable income of the teacher' is an example of
a. a dependent variable.
b. a confounding variable.
c. a response variable.
d. a normal variable.
Q. 4A researcher asked random samples of 50 kindergarten teachers and 50 12th grade teachers how much of their own money they spent on school supplies in the previous school year. They wanted to see if teachers at one grade level spend more than teachers at the other grade level. In this study, the reply to the question about amount spent on school supplies is an example of
a. a randomly assigned treatment.
b. an explanatory variable.
c. a response variable.
d. a normal variable.
Q. 5A researcher asked random samples of 50 kindergarten teachers and 50 12th grade teachers how much of their own money they spent on school supplies in the previous school year. They wanted to see if teachers at one grade level spend more than teachers at the other grade level. In this study, the grade level taught (kindergarten or 12th grade) is an example of
a. a randomly assigned treatment.
b. an explanatory variable.
c. a response variable.
d. a normal variable.
Q. 6Decide if the study is an observational study or an experiment. One hundred adults who had either Type 1 or Type 2 diabetes were randomly divided into 2 groups to determine if the inhalable version of insulin is able to manage blood sugar levels just as well as injected insulin.
a. Observational Study
b. Experiment
Q. 7Decide if the study is an observational study or an experiment. To investigate how trans fat consumption might affect fertility, researchers analyzed data available from 18,555 healthy women who participated in the Nurses' Health Study between 1991 and 1999 .
a. Observational Study
b. Experiment
Q. 8Decide if the study is an observational study or an experiment. A sample survey of 100 voters was used to compare the proportion of women in the Democratic and Republican parties.
a. Observational Study
b. Experiment
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