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1/04/2023 Tom Cockburn Wintech 2003 1
Lecture 8
Experimental research method
1/04/2023 Tom Cockburn Wintech 2003 2
Experimental method
 Experimental research is a comparison-between-
groups.
 The experimenters are seeking to discover or
corroborate cause and effect relationships by
changing something to see if the change causes a
difference to another thing.
 They alter the independent variable (IV) to see if
it causes a difference to a dependent variable
(DV).
1/04/2023 Tom Cockburn Wintech 2003 3
 A Classic, experimental method involves
assigning subjects at random to either an
‘experimental’ group or a ‘control’ group.
 The ‘control’ group is compared with the
‘experimental’ group to assess the effects of
the experiment on the experimental group.
1/04/2023 Tom Cockburn Wintech 2003 4
Switching on the light
 The independent variable(IV) can be
likened to a light switch and the dependent
variable (DV) can be likened to a light bulb.
 An experiment compares the results of
exposure of one (independent) variable
upon another (the dependent variable).
 Switch on (the IV ‘switch’) and the (DV)
bulb (metaphorically) illuminates the room.
1/04/2023 Tom Cockburn Wintech 2003 5
Advantages of experimental
research methods
 The experiment is probably the best scientific
method for attempting to prove or corroborate
causal relationships.
 It allows us to locate the variables which control
or cause a problem to occur.
 For some researchers such as those in the physical
sciences the experiment has good internal validity
because of the degree to which all ‘extraneous’
variables are controlled.
1/04/2023 Tom Cockburn Wintech 2003 6
The experimental process
 Consider-as a group-how we could set up an
experiment to discover the impact of noise
upon the recall of radio news.
 How could we test the hypothesis that noise
affects recall of radio news?
 What would we need?What is the IV
‘switch’? What is the DV ‘light bulb’ being
switched on/off?
1/04/2023 Tom Cockburn Wintech 2003 7
The noise hypothesis –1
experimental procedure
1. Select two groups. (caveats/qualifiers?)
2. Expose them to the same news broadcast.
3. One is under ‘noisy condition’ and other is
under ‘silent condition’.(definitions?)
4. After exposure to the news each group is
tested separately,using same recall
test.(test admin. Issues= ?)
5. IV=noise and DV=recall of news content.
1/04/2023 Tom Cockburn Wintech 2003 8
Aims of experimental research
 Establish cause and effect relationships.
 Then, like a switch we can turn the phenomena
‘on’ and ‘off’.
 This is useful as the ability to switch things on or
off means, a) we can be reasonably confident
we’ve found variables that cause or impact on the
problem significantly, and b) we can use that
knowledge to control or adjust such phenomena.
 Such knowledge has advanced natural science and
medicine as mentioned.
1/04/2023 Tom Cockburn Wintech 2003 9
Issues in any experimental
research
 Internal validity--This is summed up in the following
question -Does the experiment test what we say it tests?
 How sure can we be that the changes in the DV we
measured were caused by the changes in the IV?
 Are all extraneous variables or ‘confounding’ variables (ie
one which changes as IV changes) controlled?
For example, how sure can we be about the ‘noise’ and
recall of news experiment’s internal validity?
1/04/2023 Tom Cockburn Wintech 2003 10
Possible alternative explanations
or extraneous variables?
 Boredom-don’t listen to news normally and not
interested in the experiment.
 Nothing else to do-cognitive dissonance ie make it
seem better use of time/less of a waste of valuable
time?
 Trying to curry favour by participating in
teacher’s test
 Hawthorne effect.
 Non-aural learner eg visual or tactile or sociable
1/04/2023 Tom Cockburn Wintech 2003 11
 External validity means how strong are the
generalizations we can make from this
research (if any)?
1/04/2023 Tom Cockburn Wintech 2003 12
Threats to validity of
experiments
Campbell in Bynner & Stribley (1978) identified 9
threats to internal validity and 6 to external
validity.
Internal validity threats
1. History : mediating event or factor between pre-
and post-test= alternative possible explanation
of effects.e.g. Easterby and Ashton’s study of
University Management Development
Programme’s Impact on students’ careers.
(Managers’ Colleagues used absences to their own advantage).
1/04/2023 Tom Cockburn Wintech 2003 13
More threats to internal
validity of experiments
2. Maturation:changes in subjects or society such
as growth,fatigue, social trends.
3. Instability:instability of measures, sampling
fluctuations or of repeated or ‘equivalent’
measures.
4. Testing:The effect of taking a first test upon a
second or subsequent test or the effects of one
social indicator upon future readings of that
indicator e.g. ‘priming’ subjects ,stock prices.
1/04/2023 Tom Cockburn Wintech 2003 14
Even more threats
5. Instrumentation:changes in calibration of
equipment, or observers, or scores used.
6. Regression artifacts: so-called ‘pseudo-shifts’
which occur when people or treatment units
have been selected upon the basis of their
extreme scores.ie. Regression to the ‘norm’ or
middle scores in following groups or years eg
selection of years of droughts or floods or high
fatality years-following years may show
improvement even if ‘untreated’.
1/04/2023 Tom Cockburn Wintech 2003 15
Yet other threats
7. Selection: bias resulting from differential
recruitment of comparison groups-leads
to different mean scores for measures of
effects.
8. Experimental mortality: Loss of people
from comparison groups ( they die, they
move, they get new jobs etc).
1/04/2023 Tom Cockburn Wintech 2003 16
Finally--Interactive threat to
validity
9. Selection-maturation interaction:
selection biases resulting in different rates
of maturation or autonomous change. Eg
on e group matures quicker than another
causing selection bias.
1/04/2023 Tom Cockburn Wintech 2003 17
Threats to external validity
and interpretation of results
1. Interaction effects of testing- ‘priming’.
2. Interaction of selection and ‘treatment’-
unduly ‘responsive’ outcomes.
3. Reactive effects- ‘articifiality’ &
‘Hawthorne’.
4. Multiple treatment interference-
cumulative effects untypical of separate
treatment eg First Gulf war syndrome
1/04/2023 Tom Cockburn Wintech 2003 18
5. Irrelevant responsiveness measures-
complex measures,some irrelevant ones
may appear to produce effects.
6. Irrelevant replicability of treatments-
complex treatments & replications may
‘forget’/omit some components actually
responsible for the effects.
1/04/2023 Tom Cockburn Wintech 2003 19
Social science experiments
 Asch(1955)-Opinion & social pressure
 Ekman et al (1987)-Universals & cultural
differences in judgments of facial expressions of
emotion.
 Milgram (1964)-Obedience to authority
 Gordon(1992)Treatment of depressed women by
nurses.
 Zimbardo(1974)-psychology of imprisonment

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Experimental_research

  • 1. 1/04/2023 Tom Cockburn Wintech 2003 1 Lecture 8 Experimental research method
  • 2. 1/04/2023 Tom Cockburn Wintech 2003 2 Experimental method  Experimental research is a comparison-between- groups.  The experimenters are seeking to discover or corroborate cause and effect relationships by changing something to see if the change causes a difference to another thing.  They alter the independent variable (IV) to see if it causes a difference to a dependent variable (DV).
  • 3. 1/04/2023 Tom Cockburn Wintech 2003 3  A Classic, experimental method involves assigning subjects at random to either an ‘experimental’ group or a ‘control’ group.  The ‘control’ group is compared with the ‘experimental’ group to assess the effects of the experiment on the experimental group.
  • 4. 1/04/2023 Tom Cockburn Wintech 2003 4 Switching on the light  The independent variable(IV) can be likened to a light switch and the dependent variable (DV) can be likened to a light bulb.  An experiment compares the results of exposure of one (independent) variable upon another (the dependent variable).  Switch on (the IV ‘switch’) and the (DV) bulb (metaphorically) illuminates the room.
  • 5. 1/04/2023 Tom Cockburn Wintech 2003 5 Advantages of experimental research methods  The experiment is probably the best scientific method for attempting to prove or corroborate causal relationships.  It allows us to locate the variables which control or cause a problem to occur.  For some researchers such as those in the physical sciences the experiment has good internal validity because of the degree to which all ‘extraneous’ variables are controlled.
  • 6. 1/04/2023 Tom Cockburn Wintech 2003 6 The experimental process  Consider-as a group-how we could set up an experiment to discover the impact of noise upon the recall of radio news.  How could we test the hypothesis that noise affects recall of radio news?  What would we need?What is the IV ‘switch’? What is the DV ‘light bulb’ being switched on/off?
  • 7. 1/04/2023 Tom Cockburn Wintech 2003 7 The noise hypothesis –1 experimental procedure 1. Select two groups. (caveats/qualifiers?) 2. Expose them to the same news broadcast. 3. One is under ‘noisy condition’ and other is under ‘silent condition’.(definitions?) 4. After exposure to the news each group is tested separately,using same recall test.(test admin. Issues= ?) 5. IV=noise and DV=recall of news content.
  • 8. 1/04/2023 Tom Cockburn Wintech 2003 8 Aims of experimental research  Establish cause and effect relationships.  Then, like a switch we can turn the phenomena ‘on’ and ‘off’.  This is useful as the ability to switch things on or off means, a) we can be reasonably confident we’ve found variables that cause or impact on the problem significantly, and b) we can use that knowledge to control or adjust such phenomena.  Such knowledge has advanced natural science and medicine as mentioned.
  • 9. 1/04/2023 Tom Cockburn Wintech 2003 9 Issues in any experimental research  Internal validity--This is summed up in the following question -Does the experiment test what we say it tests?  How sure can we be that the changes in the DV we measured were caused by the changes in the IV?  Are all extraneous variables or ‘confounding’ variables (ie one which changes as IV changes) controlled? For example, how sure can we be about the ‘noise’ and recall of news experiment’s internal validity?
  • 10. 1/04/2023 Tom Cockburn Wintech 2003 10 Possible alternative explanations or extraneous variables?  Boredom-don’t listen to news normally and not interested in the experiment.  Nothing else to do-cognitive dissonance ie make it seem better use of time/less of a waste of valuable time?  Trying to curry favour by participating in teacher’s test  Hawthorne effect.  Non-aural learner eg visual or tactile or sociable
  • 11. 1/04/2023 Tom Cockburn Wintech 2003 11  External validity means how strong are the generalizations we can make from this research (if any)?
  • 12. 1/04/2023 Tom Cockburn Wintech 2003 12 Threats to validity of experiments Campbell in Bynner & Stribley (1978) identified 9 threats to internal validity and 6 to external validity. Internal validity threats 1. History : mediating event or factor between pre- and post-test= alternative possible explanation of effects.e.g. Easterby and Ashton’s study of University Management Development Programme’s Impact on students’ careers. (Managers’ Colleagues used absences to their own advantage).
  • 13. 1/04/2023 Tom Cockburn Wintech 2003 13 More threats to internal validity of experiments 2. Maturation:changes in subjects or society such as growth,fatigue, social trends. 3. Instability:instability of measures, sampling fluctuations or of repeated or ‘equivalent’ measures. 4. Testing:The effect of taking a first test upon a second or subsequent test or the effects of one social indicator upon future readings of that indicator e.g. ‘priming’ subjects ,stock prices.
  • 14. 1/04/2023 Tom Cockburn Wintech 2003 14 Even more threats 5. Instrumentation:changes in calibration of equipment, or observers, or scores used. 6. Regression artifacts: so-called ‘pseudo-shifts’ which occur when people or treatment units have been selected upon the basis of their extreme scores.ie. Regression to the ‘norm’ or middle scores in following groups or years eg selection of years of droughts or floods or high fatality years-following years may show improvement even if ‘untreated’.
  • 15. 1/04/2023 Tom Cockburn Wintech 2003 15 Yet other threats 7. Selection: bias resulting from differential recruitment of comparison groups-leads to different mean scores for measures of effects. 8. Experimental mortality: Loss of people from comparison groups ( they die, they move, they get new jobs etc).
  • 16. 1/04/2023 Tom Cockburn Wintech 2003 16 Finally--Interactive threat to validity 9. Selection-maturation interaction: selection biases resulting in different rates of maturation or autonomous change. Eg on e group matures quicker than another causing selection bias.
  • 17. 1/04/2023 Tom Cockburn Wintech 2003 17 Threats to external validity and interpretation of results 1. Interaction effects of testing- ‘priming’. 2. Interaction of selection and ‘treatment’- unduly ‘responsive’ outcomes. 3. Reactive effects- ‘articifiality’ & ‘Hawthorne’. 4. Multiple treatment interference- cumulative effects untypical of separate treatment eg First Gulf war syndrome
  • 18. 1/04/2023 Tom Cockburn Wintech 2003 18 5. Irrelevant responsiveness measures- complex measures,some irrelevant ones may appear to produce effects. 6. Irrelevant replicability of treatments- complex treatments & replications may ‘forget’/omit some components actually responsible for the effects.
  • 19. 1/04/2023 Tom Cockburn Wintech 2003 19 Social science experiments  Asch(1955)-Opinion & social pressure  Ekman et al (1987)-Universals & cultural differences in judgments of facial expressions of emotion.  Milgram (1964)-Obedience to authority  Gordon(1992)Treatment of depressed women by nurses.  Zimbardo(1974)-psychology of imprisonment