STRATEGIES OF RESEARCH DESIGNholds that disruption encourages children to join
deviant peer groups, which are not socialized to the
norms of work and thrift. Another theory empha-
sizes the impact of the disruption on childhood
depression and poor academic performance. In the
second theory, depression and limited school learn-
ing directly cause poor job performance.
In one study, we usually test only one or a few
parts of a causal chain. For example, a research
project examining six variables may take the six
from a large, complex theory with two dozen vari-
ables. Explicit links to a larger theory strengthen
and clarify a research project.Causal Theory and Hypotheses
The Hypothesis and Causality.A causal hypoth-
esisis a proposition to be tested or a tentative state-
ment of a relationship between two variables.
Hypotheses are guesses about how the social world
works; they are stated in a value-neutral form.
Kerlinger (1979:35) noted that,
Hypotheses are much more important in scientific
research than they would appear to be just by know-
ing what they are and how they are constructed.
They have a deep and highly significant purpose of
taking man out of himself.... Hypotheses are
powerful tools for the advancement of knowledge,
because, although formulated by man, they can be
tested and shown to be correct or incorrect apart
from man’s values and beliefs.A causal hypothesis has five characteristics
(see Expansion Box 4, Five Characteristics of
Causal Hypotheses). For example, we can restate
the hypothesis that attending religious services
reduces the probability of divorce as a prediction:
Couples who attend religious services frequently
have a lower divorce rate than do couples who rarely
attend religious services. We can test the prediction
against the empirical evidence. We should logicallyconnect the hypothesis to a research question and
to a broader theory; after all, we test hypotheses to
answer the research question or to find empirical
support for a theory. Statements that are logically
or necessarily true, or questions that are impossible
to answer through empirical observation (e.g., What
is the “good life”? Is there a God?) are not scientific
hypotheses.
We can state causal hypotheses in several ways.
Sometimes we use the word cause,but it is not nec-
essary. For example, we can state a causal hypoth-
esis between religious attendance and a reduced
likelihood of divorce in ten different ways (see
Example Box 4, Ways to State Causal Relations).
In scientific research, we avoid using the term
provedwhen talking about testing hypotheses. Jour-
nalism, courts of law, and advertisements use the
word proof,but a research scientist almost never
uses it. A jury says that the evidence “proves” some-
one guilty, or a television commercial will state,
“Studies prove that our aspirin cures headaches
the fastest.” This is not the language of scientific
research. In science, we recognize that knowledge
is tentative and that creating knowledge is an ongo-
ing process that avoids premature closure. The word
proofimplies finality, absolute certainty, or some-
thing that does not need further investigation. It is
too strong a term for the cautious world of science.
We might say that the evidence supports or con-
firms, but does not prove, the hypothesis. Even after
hundreds of studies show the same results, such asCausal hypothesis A statement of a causal expla-
nation or proposition that has at least one indepen-
dent and one dependent variable and has yet to be
empirically tested.EXPANSION BOX 4
Five Characteristics of Casual Hypotheses- They have at least two variables.
- They express a causal or cause–effect relationship
between the variables. - They can be expressed as a prediction or an expected
future outcome. - They are logically linked to a research question and
a theory. - They are falsifiable; that is, they are capable of being
tested against empirical evidence and shown to be
true or false.