Example of Probability Plot

A scientist for a company that manufactures processed food wants to assess the percentage of fat in the company's bottled sauce. The advertised percentage is 15%. The scientist measures the percentage of fat in 20 random samples. Previous measurements found that the population standard deviation is 2.6%.

As part of the initial investigation, the scientist creates a probability plot to check for normality and to evaluate the distribution.

  1. Open the sample data, FatContent.MTW.
  2. Choose Graphs > Probability Plot > Single Y Variable: Simple.
  3. In Y variable, enter Percent Fat.
  4. Click OK.

Interpret the results

The data points are relatively close to the fitted normal distribution line. The p-value is greater than the significance level of 0.05. Therefore, the scientist fails to reject the null hypothesis that the data follow a normal distribution.

Summary Statistics
N
Mean
StDev
Minimum
Maximum
Anderson-Darling Test
AD-Value
P-Value
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