Unformatted text preview: Issues To Consider with
Experiments
Experiments The Placebo effect – fake treatment used
as a control in an experiment (e.g., sugar
pills) that often gets results as well
pills) – Strangely, in many studies, a certain
Strangely,
percentage of people who don’t get the
treatment say that they feel better anyway
treatment
– This may be due to the simple attention to the
This
problem or possibly even to the release of
endorphins when you believe something
endorphins
will make you feel better Issues To Consider with
Experiments
Experiments Random assignment – each individual
has the same probability as any other in
being assigned to the experimental or
control conditions
control
– Why is it necessary that this happens in an
Why
experiment?
– What if we chose groups based on some
What
variable such as gender or ethnic group?
variable Issues To Consider with
Experiments  II
Experiments Blind and doubleblind studies – experiments
done where either or both the experimenter and/or
the subjects don’t know which group they are in
(experimental or control)
(experimental
– E.g., AIDS drugs – have to know if they work, so need a
E.g.,
control group. Single blind study – subjects don’t know which group they’re in Double blind study – neither subjects nor experimenters know
Double
which group is which (i.e., which group is getting the treatment
and which is not
and Statistics
Statistics Descriptive statistics – sum up the data
– Mean – the average of a bunch of numbers
– Median – when ordering scores from highest to
Median
lowest, the value of the middle number
lowest,
– Mode – the most frequently occurring score Statistics – II Standard deviation – the average difference
between scores in a distribution and the
distribution’s mean
distribution’s
– This is easiest to see on a normal curve Statistics – III Normal curve – represents a normal distribution
represents
– Also called a ‘bell curve’
– Represents many phenomena in science (e.g., IQ, scores on a
Represents
given test, height, weight)
given – Some notable qualities of the normal distribution: The mean is also its mode and median.
The
mode
median 68% of the area under the curve is within one standard
68%
deviation of the mean. 95% of the area is within two standard deviations.
95% 99% of the area is within three standard deviations.
99% 99.99% of the area is within four standard deviations.
99.99% Statistics – III – Normal Curve
Statistics Statistics – IV Significance testing
– Answers the question – “Would this finding ever
Answers
happen by chance?”
happen
– “Significance” is reached by getting results
Significance”
where the probability of the result happening by
coincidence (chance) is less than 5 chances in
100.
100. Statistics V  Correlations
Statistics A correlation is a measure of the strength of two
correlation
events, characteristics, behaviors, etc.
– E.g., lots of running is correlated with knee problems
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This note was uploaded on 10/03/2013 for the course SOCI 1000 taught by Professor Tim during the Fall '13 term at CUHK.
 Fall '13
 tim

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