Chapter 7: Research Design
Research Methods in Athletic Training (Arnold et. al.)
I.
Internal Validity
a.
b.
i.
II.
Threats to Internal Validity (8)
a. History
i.
ii. Example(s):
b. Maturation
i.
ii. Example(s):
c. Testing
i.
ii. Example(s):
d. Selection Bias
i.
ii.
e. Statistical Regression
i. Shifting of data toward the mean (average) as a result of 2 things:
1. Extreme group scores
a.
b.
2. Reliability or unreliability of measures
a.
f. Experimental Mortality
i.
1.
ii. Cause(s):
g. Instrumentation
i.
ii.
h. Selection Interactions
i. Interactions can compound effects of history, maturation, morality, and
instrumentation
1. Selection-history interxn –
2. Selection-mortality interxn –
1
III.
Strategies to counteract threats to internal validity (6)
a. Random Assignment
i.
ii.
1.
2. When control group is not possible,
b. Statistical Controls
i.
1. Example(s):
ii.
1. Example(s):
c. Matched Pairs
i.
1. Example(s):
ii.
1. Example(s):
d. Placebos
i.
1.
ii. Placebo ≠ Control
1.
2.
e. Blinding
i. Two types
1. Single-blind
a.
2. Double-blind
a.
b.
f. Subject Characteristics
i.
ii. Example(s):
2
IV.
Basic Research Designs (Table 7-1, p. 87)
a. Differ in 4 major ways:
i. How many groups are studied
ii. How many subjects are assigned to groups
iii. When the measures are taken
iv. How many measures are taken
b. Pre-experimental Designs – participants are not assigned to either a control or
experimental group
i. One-shot
1.
2.
3.
ii. One-group Pretest-Posttest
1.
2.
3.
iii. Static group comparison
1.
2.
3.
iv. Experimental Designs – establish cause and effect between Tx and
measurement of interest by using control groups and random assignment
v. Randomized Group
1.
a.
2.
vi. Pretest-Posttest Randomized Groups
1.
2.
3.
a. Remember
4.
a.
b.
5.
6. Disadvantages
a.
b.
c.
c. Quasi-experimental Designs – attempt to apply experimental principles to the
field setting; commonly use multiple groups and multiple observations after a
single observation
i. Nonequivalent Control Group
1.
2.
3
a.
3.
ii. Time Series
1.
2.
a. Figure 7-2, p. 92
3.
4.
iii. Reversal
1.
a. Figure 7-3, p. 93
2.
3.
a.
d. Single-Subject Designs
i.
ii.
e. Nonexperimental Designs
i. Establishes a relationship between 2 variables using statistical techniques
1.
2.
ii.
V.
External Validity
a.
b. Generalizability =
VI.
Threats to External Validity (4)
a. Multiple Treatment Interference
i.
1.
2. Example(s):
b. Interactive Effects of Testing
i.
ii.
iii.
c. Selection-Treatment Interaction
i.
ii.
d. Reactive Effects of Experimental Arrangements
i.
ii.
iii.
4
VII.
Solutions to Common Problems
a. How do I control fatigue and practice effects?
i. To prevent fatigue, make sure that appropriate time intervals occur
between measurements
ii. To prevent practice effects, include familiarization sessions prior to data
collection to assure the learning of the task is complete
iii. Counterbalancing to minimize/equalize fatigue and practice effects
1. Alternate the order of Tx to insure they occur equally at all time
points
b. Can randomization fail?
i. No. It ensures that any differences that do exist between groups is random
ii. Random assignment does not ensure that the groups will be exactly the
same, just that the differences will be random
c. When should I blind a study?
i. Participants should be blinded any time a placebo is used
ii. Researchers should be blinded any time they could have an effect on the
Tx or be biased by knowledge of the results
VIII.
Summary
a. Goal =
i. Minimize threats to internal and external validity
5