Question

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. B In an observational study a random sample is always taken from the population, whereas in a randomized experiment volunteers are always used. C In an observational study treatments are not randomly assigned, whereas in a randomized experiment treatments are randomly assigned. D In an observational study a control group is never used, whereas in a randomized experiment a control group is always used. E An observational study can be double-blind, whereas a randomized experiment can only be single-blind because the experimenter determines who is randomly assigned to each treatment.

Answer 1

A researcher carries out an experiment to demonstrate a fact or make a

discovery, or gain insight into a subject.

The element that distinguishes an observational study from a randomized

experiment is D. In an observational study a control group is never used,

whereas in a randomized experiment a control group is always used.

Reasons:

An observational study is a study focused on observing an impact of a

cause such as a treatment, test, factor of risk, while not making effort to

control or change the subjects of the impact. The researcher does not

make attempt in affecting the subjects of the experiment but measures the

effect.

Therefore;

• A randomized experiment does not use a control groups used

A randomized experiment, involves dividing the sample under study into

two;

1. A group that receives the treatment, known as the treatment group
2. A control group that will not be subject to the treatment

Therefore;

• A treatment group is always used in a randomized experiment

The correct option is D. In an observational study a control group is never

used, whereas in a randomized experiment a control group is always used.

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