Research Design &
Scales of Measurement
Research process:
1) ask research question(s)
2) develop hypotheses
3) collect the data
4) analyze the data
5) evaluate the hypotheses
Asking research questions
-
Does gun control reduce violent
crime? If so, how much?
-
What types of people are
most likely to vote?
-
What causes economic booms
or busts?
-
How many heroin addicts live
in Pierce County?
-
At what age do people first
have sex?
-
sources - personal interest,
government or nonprofit agency, interest group, business, scientific literature
(empirical and theoretical)
Developing hypotheses
-
specific predictions for
empirical research derived from theory or other sources
-
one source = theory
-
statement of why and how
several or more concepts are related
-
abstract, applies to multiple
empirical cases
-
complex or simple
-
suggests predictions
-
falsifiable
-
exploratory research - no
specific hypotheses
-
accumulated empirical research
---> theory
Collecting data
Populations, samples,
and sampling:
-
population = set of all individuals,
groups, organizations, objects, locations, time periods, or events of interest
for your study
-
e.g., pregnant women; Fortune
500 companies; adults in U.S.
-
sample = subset of pop. actually
observed
-
sampling
-
probability - each element
or unit of a population has known chance of being selected
-
often involves random selection
-
nonprobability - not possible
to specify the likelihood an element or unit will be selected for the sample
| Population |
Sample |
Sample type |
| pregnant
women |
every other
pregnant woman in 3 Tacoma clinics |
|
| Fortune
500 |
Fortune
500 cos. in WA |
|
| adults in
U.S. |
random sample
of adults in households w/ telephones |
|
-
population of interest vs. population
to which sample can generalize
Variables and measurement
-
variable = characteristic that can
take on more than one value
-
values = numbers or symbols
Scales of measurement determine
which statistical techniques are appropriate
Warning: be careful w/ numeric coding
of nominal and ordinal scale data!
Scales of measurement form a hierarchy:
interval
ordinal
nominal
-
general rule: use highest scale of
measurement possible (most information)
| scale |
key feature |
comparisons
betw. values |
| interval |
distance |
different?
which larger? how much larger? |
| ordinal |
order |
different?
which larger? |
| nominal |
quality |
different? |
-
nominal = qualitative
-
ordinal/interval = quantitative
Summary
-
research process
-
asking research questions - sources
-
developing hypotheses
-
theory
-
exploratory research
-
collecting data
-
populations, samples, sampling
-
variables
-
scales of measurement