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Descriptive statistics in social sciences
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04/10/2023 CEDP321 Ryan Sain, Ph.D. 1
Developmental Research MethodsTopic 4: Numerical Description
04/10/2023 CEDP321 Ryan Sain, Ph.D. 2
Properties of Scales• Measuring Variables–Personality; IQ, etc
• Magnitude–Size, Quantity
• Equal intervals–Equal distance between
points in terms of concept• Absolute zero–This is nothing. Noting of
the property being measured exists.
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Scales of Measurement• Nominal– Mutually exclusive
categories• Ordinal– Order of the numbers
mean something– Magnitude – but no
zero point and no equal intervals
• Interval– Magnitude– Equal intervals– No absolute zero
• Ratio– Equal intervals and a
true zero point and magnitude
The scale you are using – determines what types of statistics you can do on the data!
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DistributionsAllow you to see
how your data looks◦ Ranges or bins
(class interval)◦ 10 or 20 ranges to
cover the entire data set
You can see how skewed the data is
Allows you to decide what stat to use
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Distributions
5 to 10
11 to 15
16 to 20
21 to 25
26 to 30
31 to 35
36 to 40
0
1
2
3
4
5
Mean Alcohol Consumption by Age
mean alcohol consumption
Age
Avera
ge D
rin
ks p
er
Week
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Distributions - Skew
5 to 10
11 to 15
16 to 20
21 to 25
26 to 30
31 to 35
36 to 40
0
1
2
3
4
5
6
mean alcohol consumption
mean alcohol consumption
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Measures of central tendency
MeanMedian
◦Insensitive to extreme scores
mode
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Variation Variability in your data Range Sum of the Squared Deviations from the
Mean
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Variance and Standard DeviationVariance
Standard Deviation
or €
=SS
n
€
SD =SS
n
€
SD = var iance
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Standard scoresZ score
€
z =x −M
SD
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CorrelationRelationship between two
variablesNo causation!
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Positive Correlation
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Negative Correlation
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No correlation
