Liquid Testing | 121
ELx800 Operator's Manual
Select Tools|Data Analysis|Regression. Identify column X as the
“Input X Range” and column Y as the “Input Y Range” and then click
OK to perform the analysis.
Note: If the Data Analysis command is not available on the Tools
menu, you may need to install the Analysis ToolPak in Microsoft
®
Excel. Consult Excel’s help system for assistance.
Expected Results:
Since it is somewhat difficult to achieve high pipetting accuracy when
conducting linear dilutions, an R-Square value greater than or equal to
0.990 is considered adequate.
Repeatability Test
1 Calculate the mean and standard deviation for the five readings taken
above at each concentration. Only one data set needs to be analyzed for
each concentration. The well that shows the most variation for each
concentration is selected for data reduction.
2 For each mean below 2.000 OD, calculate the allowed deviation using
the repeatability specification for a 96-well format of ± 0.5% ± 0.005 OD
from 0.000 to 2.000 OD @ 405 nm.
3 The standard deviation for each set of readings should be less than the
allowed deviation.
For example:
Absorbance readings of 1.950, 1.948, 1.955, 1.952, and 1.950 will result in
a mean of 1.951, and a standard deviation of 0.0026. The mean (1.951)
multiplied by 0.5% (1.951 * 0.005) = 0.0098, which, when added to the
0.005 (0.0098 + 0.005) = 0.0148 OD, which is the allowable deviation.
Since the standard deviation is less than this value, the reader meets the
test criteria.
Repeatability Specification:
For comparison in this test, the following repeatability spec is applied,
using Normal mode, 96-well microplate:
± 0.5% ± 0.005 OD from 0.000 to 2.000 OD @405 nm
To Next Page
