73 – Various Topics in Statistical Education
Do Normal Probability Plots Tell the Truth When Sample Size Is Small?
Ananda Jayawardhana
Pittsburg State University
Most of the modern introductory statistics books discuss the use of normal probability plots for informal
assessment of the normality of a set of data. Textbook authors describe that if the population which the
data came from is normal, then the pattern of the points should be reasonably close to a straight line
and the pattern should not have a symmetric pattern that is not a linear pattern. Recognizing the
pattern is a subjective decision. It is well-known that normal probability plots should be interpreted
loosely for small sample sizes but usually strictly for large sample sizes. How large is large? Peck and
Devore (2012) discuss using the correlation test to check for normality. In this paper, author will discuss
an assignment he has given to the elementary statistics students and the lessons learned. Also the
author will discuss the results of a simulation study using correlation test for normality for small sample
sizes when the population is not normal.
