Health Sciences 2801A/B Chapter Notes - Chapter 3: Standard Deviation, Standard Score, Saber Of London
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An observed score is a number yielded by a measurement instrument. An observed score, however, has little practical meaning without knowing its place among other scores. The mean is a useful benchmark for judging the place of a score among other scores. A centered score is calculated by subtracting the mean from an observed score. A centered score is positive when it is above the mean and negative when it is below mean. A person"s notion of what is usual provides an important benchmark for interpreting events. It is relatively large deviation that concern us most. A variable is a set of scores that differ to some extent. A simple measure of variability is the sum of squares. It is calculated by squaring the centered scores and adding them together. A sum of squares is larger when the scores fall farther from the mean and smaller when the scores fall nearer to the mean.