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AP Psychology Review
Your Topics of Choice
2011-2012
UNIT TWO: RESEARCH METHODS
Measures of Central Tendency
“a measure of central tendency is a single score
that represents a whole set of scores”
• mean
arithmetic average
• median
middle score/midpoint
• mode
most frequently occurring score
An example:
Data Set:
1,1,1,2,2,6,7,9,10
What is the mean? 4.3
the median?
2
the mode?
1
Range and Standard Deviation
Averages that come from scores with low variability
are more reliable than those from scores with high
variability.
So how do we know?
range- gap between lowest and highest
standard deviation- measures how much scores
deviate from one another/from the mean
When there is a lot of variability, the standard
deviation will be large; when variability is
smaller, the standard deviation will be smaller.
Variability
35
30
25
20
Series 1
15
Series 2
10
5
0
10
20
30
40
50
60
70
80
90
100
Calculating the Variance
1. determine the mean
2. determine the difference between each score
and the mean (the deviation)
3. square each deviation
4. calculate the mean of the squared deviations
To get the standard deviation, simply take the
square root of the variance.
Which of the following is true of the two sets of scores in
the chart?
a. Set A has a larger standard deviation.
b. Set B has a larger standard deviation.
c. The range is the same for both distributions.
d. Set A has a lower median score than set B.
e. The mean score is the same for both distributions.
Set A
Set B
60
56
58
62
61
59
60
41
76
35
65
50
25. For a language test with normally distributed
scores, the mean was 70 and the standard
deviation was 10. Approximately what
percentage of test takers scored 60 and
above?
a. 16
b. 34
c. 68
d. 84
e. 95
63. Which of the following sets of scores has the
greatest standard deviation?
a. 5,7,9,12
b. 2,7,9,22
c. 25,27,29,32
d. 50,51,52,53
e. 100,101,101,102,103
rational-emotive therapy
• An approach to therapy that focuses on
altering clients’ patterns of irrational thinking
to reduce maladaptive emotions and behavior
• “you feel the way you think” (Albert Ellis)