Widget: Calculate the Critical Value for a QQ Plot

QQ Plots can be constructed to assess the normality of a set of sample data. If your sample comes from a normal distribution, the plot will be close to a straight line pattern. But, how close is close enough? If you calculate the linear correlation coefficient (r) for your QQ Plot you can compare it to the critical value generated by the Widget below.

• If r > critical value, then your sample comes from a normally distributed population.
• If r < critical value, then your sample comes from a non-normally distributed population.

You can read more about this on Stan Brown's Statistics pages.