Class Notes: Experiments
Experiments are one of many methods
available to the social scientist. Unlike all other methods, however,
experiments allow the researcher to specify cause and effect. What
are the basics of experiments?
- What defines an
experiment?
- Experimental
treatment
- procedure or substance to
investigate
- Use of at least two
groups
- control group
- experimental group
- An experiment may have many
groups
- Toothpaste example
- Does toothpaste and brushing
lead to fewer cavities?
- How can we test?
- Set up two groups, and
randomly assign to:
- control group
- brush with water
three times/day for six months
- experimental
group
- brush with
toothpaste three times/day for six months
- Measure effect of
toothpaste and water brushing with:
- number of cavities
after six months
- Make both groups have
zero cavities
- Time out for some
terminology
- Independent Variable
(IV)
- toothpaste or no
toothpaste
- Dependent Variable
(DV)
- Extraneous
Variables
- Back to the
experiment
- After six months count
cavities
- If fewer in experimental
group, you can say:
- "Toothpaste has been
proven to be an effective dentifrice when used as part of
a regular brushing program."
- Recall hypotheses
- Here hypothesis
is:
- Brushing with
toothpaste will result in fewer cavities
- More generally:
- The IV led to some
change in the DV
- Bad experiments
- Nox-Out©
- Imagine you are a
researcher for a pharmaceutical company and you are asked to
test an new drug, Nox-Out©, a new sleeping pill. For
now, here are the variables:
- IV:
Nox-Out©
- DV: some way(s) of
measuring Nox-Out©'s effects
- hours of
sleep
- quality of
sleep
- latency of
sleep
- Extraneous:
- age of
participants
- fatigue level of
participants
- hours since last
sleep
- location of
experiment
- Consider the following
situations in the Nox-Out© experiment:
- Age
- Control group has
average age of 25
- Experimental group has
average age of 75
- Results are not
valid graph
- Fatigue
- Control group members
all work as ditch diggers
- Experimental group
members all work in offices
- Hours since sleep
- Control group gets
Nox-Out© at 11:00 a.m., or five hours since
waking
- Experimental group
gets Nox-Out© at 11:00 p.m., or 16 hours since
waking
- Location of
experiment
- Control group sleeps
at the local Hilton
- Experimental group
sleeps at local dive motel
- Results are not
valid
- How to fix?
diagram
- Proper Nox-Out©
experiment
- Both groups should be the
same in all aspects except the administration of
Nox-Out©
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This page was created 1/30/01 and its address
is:
http://peace.saumag.edu/faculty/kardas/expt/basics.html
