PSYC2009 Study Guide - Quiz Guide: Richter Magnitude Scale, Continuous Or Discrete Variable, Central Tendency
Descriptive Statistics, Experimental Design and Sampling/Graph
Displays
Variables:
• Discrete: can take certain values but not others
• Continuous: Can (theoretically) take any values over their "range"
Measures of central tendency
• Mean: average score
• Median: middle score
• Mode: most common score
Measures of variability
• Range: difference between the largest and smallest values in your data set
• Standard deviation: quantifies the amount of variation in the data set.
o Low values: values close to the mean
o Large values: values more spread out
Levels of measurement
Level
Description
Example
Type of
variable
Measures of
central
tendency
Nominal
Categories that cannot be
ordered
Favourite movie, political
party and membership
Discrete
Mode
Ordinal
Categories that can be
ordered but their
differences are not
quantifiable
Military rank, Likert
scales (technically)
Discrete
Median, mode
Interval
Values on a scale where the
differences are quantifiable
but lacks a "true zero"
Celsius (0 isn't a
complete absence of
heat), Likert scales
(practically)
Discrete or
continuous
Mean, median
and mode
Ratio
Values on a scale where the
differences are quantifiable
and contains a "true zero"
Kelvin, time, weight,
Richter scale
Discrete or
continuous
Mean, median
and mode
Outliers and skew
• Outlier: value in data set that is distant from other values
• Positive skew: distributions of values has a long "tail" to the right
• Negative skew: distribution of values has a long "tail" to the left
• At least 5 ways to find out peoples behavioural or attitudinal proclivities:
1. Ask people to report their own
2. Observe directly
3. Ask people about someone else whom they know well
4. Ask people about others "in general" or "on average"
5. Find indirect observational evidence (examining peoples rubbish for evidence of
consumer habits and preferences)
Variables
• Discrete: can only take certain values ang not others. Gender is discrete variable with
two (or more) values
• Continuous: those which (theoretically) could take any value over their "range"
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