1. Chapter 4 Variability

2. Introduction Purpose of measures of variability Consider what we know if we know that the mean test score was 75 Single score to represent the spread of the entire distribution of scores Types of measures Range Interquartile range Semi-interquartile range Variance Standard deviation

3. Measures of variability Understanding central tendency and variability in the Test 1 scores In-class exercise

4. Variance and SD for a population Calculate variance and SD for the following population: X 7 6 4 3

5. SD displayed on a normal distribution Consider the population of IQ scores  =100  =15 Draw the distribution

6. Variance and SD for a sample Calculate variance and SD for the following sample: X 7 6 4 3

7. Transformations of scale How does changing all of the scores in a distribution change the measures of central tendency? In-class exercise