Unit 2 (F):
Statistics in
Psychological Research:
Measures of Central Tendency
Mr. McCormick
A.P. Psychology
Do-Now:
(In Journal)

What are statistics?

Why are statistics important in social sciences?

How are the following measures of central
tendency found?
Mean
 Median
 Mode

Statistics in Psychology

Statistics:

The collection, classification,
analysis, and interpretation of
numerical psychological data

Descriptive Statistics:
Describes collected data
 Frequency Distribution:



Bar Graph
Histogram
Statistics in Psychology

Types of Psychological Data:

Nominal:




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Categorical
Non-numerical; cannot compute mean
Bar graph
E.g. Favorite ice cream flavor
Ordinal:

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
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Ordered
Non-numerical; cannot compute mean
Bar graph
E.g. 1st place, 2nd place, 3rd place
Statistics in Psychology
Can you think of
another example of
Nominal and
Ordinal data?
Statistics in Psychology

Types of Psychological Data:

Interval:

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
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Equal interval between points;
no true zero point
Numerical; can compute mean
Histogram
E.g. Degrees in Fahrenheit
Ratio:




Equal interval between points;
true zero point
Numerical; can compute mean
Histogram
E.g. Height/weight
Statistics in Psychology
Can you think of
another example of
Interval and
Ratio data?
Measures of Central Tendency

Mean:

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
Median:



The arithmetic average of a distribution
Obtained by adding all scores together, and dividing by the
number of scores
The middle score of a distribution
Half of the scores are above it and half are below it
Mode:

The most frequently occurring score(s) in a distribution
Distributions

Normal Distribution:
Symmetrical, Bell-shaped distribution
 Mean, Median, Mode all are the same

Distributions

Skewed Distribution:
Positively skewed; “Skewed to the Right”
 Negatively skewed; “Skewed to the Left”

Distributions
 What
types of situations might cause a
“positively-skewed” distribution?
 What
types of situations might cause a
“negatively-skewed” distribution?
Distributions
Positively Skewed Distribution
Review

Differentiate between the following types of data:
Nominal
 Ordinal
 Interval
 Ratio


What is a normal distribution?

What is the difference between a positively and
negatively-skewed distribution?
Homework

Unit 2 FRQ

Unit 2 Test: “Research Methods”

Chapter 2 Outline: “The Biology of Mind”