slides third lesson - 2018 04 23 - unibg third lesson - 2018_… · z-scoredistribution •...
TRANSCRIPT
Why z-scores?
• Transforming scores in order to make
comparisons, especially when using different
scales
• Gives information about the relative standing
of a score in relation to the characteristics of
the sample or population
– Location relative to mean
– Relative frequency and percentile
What does it tell us?
• z-score describes the location of the raw score
in terms of distance from the mean, measured
in standard deviations
• Gives us information about the location of
that score relative to the “average” deviation
of all scores
Z-score Distribution
• Mean of zero
◦ Zero distance from the mean
• Standard deviation of 1• Standard deviation of 1
• Z-score distribution always has same shape as
raw score. If distribution was positively skewed to
begin with, z scores made from such a
distribution would be positively skewed.
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