Purpose: The purpose of the QQ plot is to test for normal distribution in a column of data.  Many predictive models require that the data be normally distributed.  If it is not, then the model will not work well.  This plot can help a user determine if their data is normally distributed and whether or not it should be fed into a given predictive model.


Inputs: 

  1. Data table
  2. Column


Limitations: 

  • Can only run one column at a time


Prep:


Steps to Run:

  1. Go to the Tools menu
  2. Select the Data Science option
  3. Select the QQ plot option
  4. Enter the data table and the column name the analysis should be performed on


Outputs: 

  • The output is a single scatter plot visualization.  
  • Normal Quantiles are on the x axis and the Sample Quantiles are on the y axis.  


Interpretation: 

  • If the data is normally distributed, it will fall along the line in the plot.
  • If the data is not normal, then you can apply transformations, select a subset of data, or remove outliers.