The Normal distribution (also called the Gaussian distribution or the bell curve) is frequently occuring for many continuous variables (e.g. the IQ distribution in the population). The bell shaped curve describes a probability function showing that, for a normally distributed variable, values closer to the mean are most likely to occur in the population. As the distance from the mean increases (on either side), the probability of occurance decreases. For instance, as IQ increases or decreases, the probability of occurance in the general population is gradually decreasing. The normal distribution is symmetric and has certain properties that allow predictions and the computation of standardized scores. It enables researchers to analyze and compare scores and find out the proportion of individuals who fall above or below a score. The lecture provided describes the properties of Normal distributions, demonstrates how to determine location using percentiles and z-scores, how to apply the 68-95-99.7 rule to determine proportions, and perform calculations of standardized scores.
- Diana Mindrila, Ph.D.
- Phoebe Balentyne, M.Ed.

  • The Normal Distribution Video and Notes
    Narrated Presentation: The Normal Distribution

    Download the Normal Distribution Notes [PDF]

  • Computing Z Scores (SPSS)
    Software Tutorial: Computing Z Scores (SPSS)

  • Histograms (SPSS)
    Software Tutorial: Histograms (SPSS)