To open the Grubbs' test dialog box from the menu:
Select to output results to the Results Log.
Controls recalculation of analysis results:
For more information, see: Recalculating Analysis Results
Must be a column or column range.
For help with range controls, see: Specifying Your Input Data
Select to generate an outlier plot. Scatter plot with upper and lower confidence limits and dataset mean as line plots.
Worksheet range to output the outlier plot data (available if Outlier Plot is selected). Flat sheet lists upper and lower confidence values.
For help with the range controls, see: Output Results
The worksheet range to output the report table.
1. Calculation of the Grubbs test statistic :
where is the value of suspected point (usually highest or lowest observation), is the mean value of data set, and is the standard deviation.
Compare with the critical value.
2. Calculation of the p value:
where is the largest and is the number of samples.
The p value is then calculated as the two-tailed P value for the student-t distribution of the value.
The missing values in the data range will be excluded in the analysis
Stephen L R. Ellison, Vicki J. Barwick and Trevor J Duguid. Farrant. 2009. Practical Statistics for the Analytical Scientist. The Royal Society of Chemistry, Cambridge, UK.