Why z-scores? Transforming scores in order to make comparisons, - - PowerPoint PPT Presentation

Why z-scores?

• Transforming scores in order to make

comparisons, especially when using different scales

• Gives information about the relative standing
• f 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

• f 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.

disabled

disabled disabled

disabled