Chapter 6/Scaled Scores and Standard Scores: How to Change Apples Into Oranges

Multiplying or Dividing a Constant

Multiplying or dividing a constant changes the mean and the standard deviation both. The spread of the scores change.

What are scaled scores?

-Scores that are adjusted through applying the same constant to all scores in the distribution. -The constant is either added, subtracted, multiplied, or divided to all scores. The mean and standard deviation may change, but their relative position remains the same.

Adding or Subtracting a Constant

Adding or subtracting a constant changes the mean the amount of the constant and the standard deviation remains the same.

Why are scaled scores needed?

There are many reasons to scale scores. For example - -Tests may be unusually difficult or easy and need to be adjusted for a comparison to another test. -Tests may be measured on different scales and need to have a common scale.

Standard Scores (z Scores)

Transforms scores to a distribution that has a mean of 0 and standard deviation of 1. (z distribution) -Use the transformation rules: Subtract the constant (the mean of the distribution. Divide the constant (the standard deviation of the distribution).