There are two ways in which hypotheses can be tested: a. Correlational research
This is also known as cross-sectional research
This involves observing the natural pattern or occurrence to
test
Original occurrences are not manipulated b. Experimental research
We select the variables of interest
Then we manipulate some aspect of the environment
Observe the effect on the selected variable
There are two types in variation explained as follows: Systematic variation:
Introduced by experimenter
The participants are tested under different conditions and the
difference in condition is introduced by experimenter
For Example to test use of woolen clothes w.r.t. temperature, we
can test a group of 20 people, in both hot and cold climate.
Thus, the difference introduced here is in terms of temperature
only. Unsystematic variation:
Introduced by random factors that exist between the
experimental conditions.
For Example To test use of woolen clothes w.r.t. temperature,
we can test a group of 20 people. Of the selected set some
might behave differently than expected due to factors like
illness and so on.
Same measure is measured under different conditions on
same set participants.
The difference in two conditions can be caused by the following:
The manipulation/changes that was carried out on the
participants
Factors that might affect the way in which a participant
performs from one time to the next
Same measure is measured under different conditions on
different set of participants.
The differences between the two conditions can be caused by
the following:
The manipulation/changes that were carried out on the
participants
Difference in nature or characteristics of participants in each
case
By using randomization we can ensure that any variation
introduced, is due to changes in the conditions/variables
introduced rather than any other unexpected changes during
the process. Thus, it helps in removing other sources of
systematic variation.