What do we look for in ‘Shape’?

Shape of distribution: Populations with the same mean and standard deviation can still have distributions with very different shapes.

Symmetry

• bell shaped or normal
• uniform

Skewness

• skewed to the right (skewed positively)
• skewed to the left (skewed ??? )

Modality - # of prominent peaks

• unimodal
• bimodal

Outliers

• they affect the mean!

Symmetry, Skewness, Modality

A histogram, provides a picture of the pattern of scores in a certain sample, gives us a good way to estimate the distribution of scores in the population.

Which distribution do you know that is symmetric?