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Lecture

Chapter notes


Department
Psychology
Course Code
PSYB01H3
Professor
Anna Nagy

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Chapter 9 Conducting Experiments
1
SELECTING RESEARCH PARTICIPANTS
-Recall fr Ch.7
oMost research involves sampling research participants fr a pop of interest (composed of
individuals of interest)
Using probability or non-probability sampling techniques
Imp when conducting scientific polls
-Much research interested in testing hypotheses about behaviour
oFocus here: relationships btw variables being studied and testing predictions derived fr
theories of interest
Easiest way to find people = non-probability haphazard or convenience sampling
methods
Nothing wrong with it as long as you realized they affect the ability to generalize
your result to some larger population (issues discussed in ch.14; ample of
evidence shows that with this type of sampling one can still generalize
findings….)
oSample size- increasing it will increase likelihood that your results will be statistically signif
Discussed in Ch.13 (choosing sample sizes)
MANIPULATING THE INDEPENDENT VARIABLE
-to manipulate, need to construct an operational definition (see Ch. 4); convert conceptual var into
set of operations (instructions, stimuli, events presented to participants)
-in addition, the IV and DV must be introduced within context of total experimental setting- called
“setting the stage
Setting the Stage
-2 things to do:
o(1) provide participants with informed consent needed (2) explain why experiment is being
conducted
-Sometimes rationale = truthful; most of the time, you dont want to tell participants the actual
hypothesis
oi.e. say your conducting test on memory (but actually conducted on specific aspect of memory
=DV)
if you tell them truth, they may try to look good and try to confirm the hypothesis
-Thus, if deception= necessary
oNeed to debrief ALL at conclusion of experiment
-NO clear cut rule on HOW to manipulate---depends on cost, practicality and ethics of procedures
Types of Manipulations
(1) Straightforward Manipulations
-Manipulate with relative simplicity with instructions/stimulation presentations---presenting
written, verbal or visual material to participants
-Examples (For exam purposes)www.notesolution.com

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Chapter 9 Conducting Experiments
2
o1. studying impact of health promotion brochures by asking women to read brochure on
breast self-examinations (grp 1: text only text; grp 2 text + pics); Q re: performing bres-self-
exam after reading
Women NOT comfortable w/ sexual material- less sure about ability
Women comfortable w/.- type of brochure did not affect answer
o2. Jury Studies---where a crucial piece of info (severity) is varied and affects results
In birth-control pills and cancer case: severity info affected liability judgment on pill
manufacturer
o3. Most memory research relies on this method of manipulation
Differing list (similar words: cat, map, pat vs dissimilar: mop, pen, cow); lists with
more dissimilar words are recalled more accurately
o4. British Soap opera Study: “experts and unfamiliar people of a soap are given both a
typical script and an atypical script; FOUND: being expert only helps if typical; if atypical,
fans + nonfans have = retention
o5. Study on effect of communicator credibility and personal involvement on attitude change
Manipulation of cred= prof vs. student written; manip of involvement =
implementation same yr, 10 years later
Participants in low invol changed their attitudes more if the communicator was high in
creditability
If parti highly involved, the credibility of communicator did not make a difference
(2) Staged Manipulations
-Less straightforward; as it may be necessary to stage an event during experiment in order to
manipulate IV
o= staged or event manipulation
-Used frequently for 2 reasons
o(1) to create psychological state in participants; anger, sadness, low self-esteem
o(2) in order to stimulate a situation that occurs in the real world
-Example
oStudy on performance when doing multiple tasks (1 condition: were interrupted time to time)
-Manipulation frequently employs a confederate (or accomplice)
oUsually appears to be another participant (but created particular situation for an
experiment)
oRecall the Asch experiment (announcement of incorrect ans (of line size) by all confederates
—produces conformity amongst the real participants)
omay help in field/lab experiments as well (i.e. pose as shopper in mall and asks for change)
-Some Issues
oDifficult to replicate (i.e. each procure allows for subtle interpersonal communication)
oComplex manipulations hard to interpret
oIf many things happened---what one thing was responsible for the results?
IN GENERAL
*straightforward---easier to interpret results
Strength of the Manipulation
-simplest experimental design2 levels of IV (researcher chooses)
-general principle: make manipulation as strong as possible
www.notesolution.com
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