Quartiles Report

Equal Variance Analysis

 

See Also:

Box Plot:

Bartlett's Test

Levene's Test

 

(Not to be confused with the Quantile Test)

 

Description:

 

The quartiles reports displays maximum and minimum values, and 25th, 50th, and 75th percentiles for data for each well. Statistics for the report are displayed for all wells for the selected parameter. These statistical values can be used to simplify statistical calculations beyond the capabilities of ChemStat or for verification of ChemStatcalculations.

 

The Box Plot graph is a graphical display of the values in this report. The algorithm used for the Quartile report is the same as that used for the display of the Box Plot.

 

 

Remarks:

 

The xth percentile of a distribution is the value below which x percent of the measurements lie. In many cases, the percentiles for a box plot do not produce an integer number. For example, in a distribution with 7 measurements, the 3.5th sample is the 50th percentile. The 1989 guidance recommends averaging the upper and lower values, in the case average the 3rd and 4th values in the distribution to get the 50th percentile.

 

However ChemStat implements a weighted average between measurements. In testing, calculated values differed slightly than those reported in the 1992 guidance, but matched exactly with the values obtained with Microsoft Excel(TM). The difference between the two methods is typically so small, that it should not have any noticeable effect on the box plot.