Data Collection Methods
To derive conclusions from data, we need to know how the data
were collected; that is, we need to know the method(s)
of data collection.
Methods of Data Collection
In this lesson, we will cover four methods of data collection.
- Census. A census is a study that obtains data
from every member of a
population.
In most studies, a census is not practical, because of the
cost and/or time required.
- Sample survey. A sample survey is a study
that obtains data from a subset of a population, in order
to estimate population attributes.
- Experiment. An experiment is a controlled
study in which the researcher attempts to understand
cause-and-effect relationships. The study is "controlled" in
the sense that the researcher controls (1) how subjects are
assigned to groups and (2) which treatments each group
receives.
In the analysis phase, the researcher compares group scores on
some
dependent variable.
Based on the analysis, the researcher draws a conclusion about
whether the treatment
(independent variable) had a causal effect on the
dependent variable.
- Observational study. Like experiments,
observational studies attempt to understand cause-and-effect
relationships. However, unlike experiments, the researcher
is not able to control (1) how subjects are
assigned to groups and/or (2) which treatments each group
receives.
Data Collection Methods: Pros and Cons
Each method of data collection has advantages and disadvantages.
Test Your Understanding
Problem
Which of the following statements are true?
I. A sample survey is a type of experiment.
II. An observational study requires fewer resources than an experiment.
III. The best method for investigating causal relationships is an
observational study.
(A) I only
(B) II only
(C) III only
(D) All of the above.
(E) None of the above.
Solution
The correct answer is (E). Unlike an experiment, a sample survey does not require the researcher
to assign treatments to survey respondents. Therefore, a sample
survey is not necessarily an experiment. A sample survey could be an observational study, rather than an experiment.
An observational study may or may not require fewer
resources (time, money, manpower) than an experiment. The best
method for investigating causal relationships is an experiment - not
an observational study - because an experiment features randomized
assignment of subjects to treatment groups.