Experiments vs. Observational Studies

Which of the following is a key distinction between well designed experiments and observational studies?

• More subjects are available for experiments than for observational studies.

• Ethical constraints prevent large-scale observational studies.

• Experiments are less costly to conduct than observational studies.

• An experiment can show a direct cause-and-effect relationship, whereas an observational study cannot.

• Tests of significance cannot be used on data collected from an observational study.

Which is one of the main differences between experiments and observational studies?

• There is a response variable in an experiment, but not in an observational study.

• There is at least one explanatory variable in an experiment, but not in an observational study.

• An experiment requires blocking, while an observational study does not.

• An experiment can be used to establish a causal relationship, but an observational study cannot.

• Observational studies require larger samples than experiments.

A farmer wants to see if the brand of food fed to baby pigs makes a difference. Two of his sows have a litter of 10 pigs on the same day. Litter A was given Brand A, litter B was given Brand B.

The farmer has conducted a(n)

• simple random sample.

• observational study.

• experiment, but not completely randomized.

• experiment that is completely randomized.

A researcher took a random sample of 50 people and asked them if they regularly exercised. They all reported to a clinic to have their cholesterol measured.

• Observational Study

• Experimental Study

• It is impossible to determine.

In an ________________, a researcher observes and measures characteristics of interest of part of the population but does not change existing conditions.

• Experiment

• Observational Study

One group of subjects was given an herbal supplement and another group was given a placebo. After one year, the number of illnesses each group had was compared.

• Observational Study

• Experiment

Individuals are observed and variables are measured without controlling the individuals or the environment

• population

• observational study

• experiment

• secondary data

Individuals are monitored for measures of variables of interest but not influenced in response.

• Observational Study

• Experiment

• Voluntary Response

• Single-Blind

Four groups of randomly selected people are assigned a different diet. After six months, the blood pressures of each group are compared.

• Observational Study

• Experiment

You want to see if students who have a 4.0 grade point average study more than those who do not.

• experiment

• observational study