INTRODUCTION
TO
EXPERIMENTAL
DESIGN
Comparison of concurrent and retrospective pain ratings during
rehabilitation following anterior cruciate ligament reconstruction.
Brewer et al. (2004) Journal of Sport & Exercise Psychology, 22, 610-615.
The accuracy of retrospective ratings of pain intensity was
examined in a sample of 108 participants undergoing rehabilitation
following anterior cruciate ligament surgery. Participants completed
daily ratings of current pain intensity for the first 42 days of rehab.
Participants also provided retrospective ratings of pain intensity on
Days 7 and 21 and again on Day 30.
Correlations between concurrent and retrospective pain ranged from
.74 to .88. The results suggest that retrospective pain ratings can
substitute for concurrent pain ratings if a tendency toward
overestimation is taken into account.
Injury Prevention in Sweden: Helping Soccer Players at Risk
Johnson et al. (2005) Journal of Sport & Exercise Psychology, 23, 32-38.
This study examined the effectiveness of a program to lower the
incidence of injury for soccer players identified as being at high risk
of injury.
32 high injury-risk players were identified and randomly assigned to
treatment and control groups. Injuries of participants were reported
by their coaches. The intervention program consisted of training in
6 mental skills distributed over 6 to 8 sessions.
The results showed that the brief intervention prevention program
significantly lowered the number of injuries in the treatment group
compared with the control group.
EXPERIMENTAL DESIGN
EXPERIMENTS:
An experiment is a study in which at least one
variable is manipulated and units are randomly
assigned to the different levels of the
manipulated variable(s).
Comparison of concurrent and retrospective pain ratings during
rehabilitation following anterior cruciate ligament reconstruction.
Brewer et al. (2004) Journal of Sport & Exercise Psychology, 26, 610-615.
The accuracy of retrospective ratings of pain intensity was
examined in a sample of 108 participants undergoing rehabilitation
following anterior cruciate ligament surgery. Participants completed
daily ratings of current pain intensity for the first 42 days of rehab.
Participants also provided retrospective ratings of pain intensity on
Days 7 and 21 and again on Day 30.
Correlations between concurrent and retrospective pain ranged from
.74 to .88. The results suggest that retrospective pain ratings can
substitute for concurrent pain ratings if a tendency toward
overestimation is taken into account.
Injury Prevention in Sweden: Helping Soccer Players at Risk
Johnson et al. (2005) Journal of Sport & Exercise Psychology, 27, 32-38.
This study examined the effectiveness of a program to lower the
incidence of injury for soccer players identified as being at high risk
of injury.
32 high injury-risk players were identified and randomly assigned to
treatment and control groups. Injuries of participants were reported
by their coaches. The intervention program consisted of training in
6 mental skills distributed over 6 to 8 sessions.
The results showed that the brief intervention prevention program
significantly lowered the number of injuries in the treatment group
compared with the control group.
Injury Prevention in Sweden: Helping Soccer Players at Risk
Johnson et al. (2005) Journal of Sport & Exercise Psychology, 27, 32-38.
This study examined the effectiveness of a program to lower the
incidence of injury for soccer players identified as being at high risk
of injury.
32 high injury-risk players were identified and randomly assigned to
treatment and control groups. Injuries of participants were reported
by their coaches. The intervention program consisted of training in
6 mental skills distributed over 6 to 8 sessions.
The results showed that the brief intervention prevention program
significantly lowered the number of injuries in the treatment group
compared with the control group.
EXPERIMENTS:
The independent variable is manipulated to
determine its effect on the dependent variable(s)
whilst holding all other potential influences on
the dependent variable(s) constant
One-year endurance training: Effects on lung function and airway inflammation
Denguezli, M. et al., (2008).
Journal of Sport & Exercise Psychology, 26, 1351 - 1359.
The aim of this study was to determine whether endurance training in athletes
induces airway inflammation and pulmonary function disorders. Respiratory
pattern and function were analysed in ten healthy endurance runners on three
different occasions (basic endurance training, pre-competitive and competitive
periods). Airway cell counts and inflammatory markers changed significantly. At
the beginning of the experiment, athletes' induced sputum showed an abundance
of macrophages compared with neutrophils. We found a high percentage of
neutrophils during the pre-competitive and competitive periods of the sport
season, a significant increase in macrophage counts during the pre-competitive
period, and a significant rise in total cells, interleukin-8, leukotriene E4 during
the competitive period.
Two sides to the coin:
If X, then Y
and
If not X, then not Y
ANY OTHER TYPE OF STUDY IS
NOT AN EXPERIMENT!
Antioxidant response and oxidative damage induced by a swimming session
Tauler, P. et al., (2008). Journal of Sport & Exercise Psychology, 26, 1303-1311.
In this study, we examined oxidative stress after a swimming session, the
responses of the antioxidant defences, and the influence of gender on these
responses. Fifteen boys and eight girls participated voluntarily in the study.
Plasma concentrations of 17-β-estradiol, vitamin E, retinol, carotenes,
ascorbate, malondialdehyde, and the carbonyl index were determined.
Exercise increased plasma ascorbate both in boys and in girls.
Malondialdehyde increased in boys but was maintained in girls after exercise.
Creatine kinase values corrected for lean body mass were similar in boys and
girls at baseline, but the post-exercise values in boys were higher than in girls.
In conclusion, a swimming session induced higher muscular and oxidative
damage in boys than in girls.
QUASI-EXPERIMENTS
A quasi-experiment has all the elements of
an experiment, except that participants are
not randomly assigned to groups
QUASI-EXPERIMENTS
The independent variable is not directly manipulated
by the investigator. Rather, the levels of the
independent variable are in some way naturally
occurring, or the manipulation has already occurred
through some process beyond the investigator’s
control
QUASI-EXPERIMENTS
e.g. The differential effects of exercise on
oxidative damage among males and females
We cannot randomly assign participants
to male and female groups!
We can compare males and females in their
responses to exercise
Non-equivalent control group design
Are participants randomly
assigned to groups or conditions?
yes
True experiment
TYPES OF
DESIGN
no
Is there a control or
comparison group, or
multiple conditions?
yes
Quasi-experiment
no
Pre-experiment
Relaxation and recovery from anaesthesia
Pre-operative anxiety can increase the time taken for patients to recover
from anaesthesia for surgery. A study was conducted to determine whether
a brief pre-operative relaxation procedure could reduce recovery time in
surgical patients with sports injuries. Athletes about to undergo three
different types of surgery were assigned to one of three conditions. Those
about to receive a steroid injection for frozen shoulder were assigned to a
relaxation condition in which they listened to a 30 min. relaxation tape
immediately prior to transfer to the operating theatre. Athletes about to
undergo repair of ruptured anterior cruciate ligament were assigned to a
placebo condition in which they listened to a 30 min. tape-recorded short
story. Athletes about to undergo reduction of dislocated shoulder acted
as no-treatment controls. Results showed that, when controlling for the
amount of time spent under anaesthesia, the relaxation group took
significantly less time to recover than either of the other two groups and
the no-treatment control group took significantly less time than the placebo
group. The results suggest that the relaxation treatment is an effective
means of reducing recovery time whilst listening to a short story may
actually increase recovery time.
TRUE EXPERIMENTAL DESIGNS
What is the purpose of randomisation?
To ensure that groups
are equivalent with
regard to everything
except their exposure
to the different levels
of the independent
variable
PRETEST-POSTTEST CONTROL GROUP DESIGN
VO2 max
Experimental group
Control group
Pre-test
Post-test
Training
PRETEST-POSTTEST CONTROL GROUP DESIGN
Three Types of Effect:
Dependent Variable
1 Within subjects
(main effect for test)
Pre-test
Post-test
PRETEST-POSTTEST CONTROL GROUP DESIGN
Three Types of Effect:
Dependent Variable
1. Within subjects
(main effect for test)
Pre-test
Post-test
PRETEST-POSTTEST CONTROL GROUP DESIGN
Three Types of Effect:
Dependent Variable
2. Between groups
(main effect for group)
Pre-test
Post-test
PRETEST-POSTTEST CONTROL GROUP DESIGN
Three Types of Effect:
Dependent Variable
2. Between groups
(main effect for group)
Pre-test
Post-test
PRETEST-POSTTEST CONTROL GROUP DESIGN
Three Types of Effect:
Dependent Variable
3. Group x test interaction
Does the effect of one
IV (test/time) depend
upon levels of a second
IV (group)
Pre-test
Post-test
Pre-test
Post-test
Dependent Variable
Pre-test
Post-test
Dependent Variable