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3-6 Probability Plots

3-6.1 Normal Probability Plots

• How do we know if a normal distribution is a reasonable

model for data?

• Probability plotting is a graphical method for determining

whether sample data conform to a hypothesized

distribution based on a subjective visual examination of the

data.

• Probability plotting typically uses special graph paper, known

as probability paper, that has been designed for the

hypothesized distribution. Probability paper is widely

available for the normal, lognormal, Weibull, and various chi-

square and gamma distributions.