Bio-Rad Model 680 Microplate Reader Accessories - Manual (Page 16)

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Blank mean = X/n
S.D. = [{X^2 – n*(Blank mean)^2}/{n-1}]^1/2
Where:
S.D. = Standard deviation
X = Sum total of the raw absorbance for each blank
X^2 = Sum total of the squared raw absorbance for each blank
n = Number of blanks
(3) Limit report
The Limit report provides a qualitative YES/NO report. Wells with blank-subtracted
absorbance values between the upper and lower limits are represented with an
asterisk (*), wells with absorbance values below the lower limit by minus signs (-),
and wells with absorbance values greater than the upper limit by positive signs (+).
(4) Matrix report
The Matrix report provides a qualitative report of the relative magnitude of the
absorbance values on the plate. The absorbance range defined by the upper and
lower limits is divided into 10 equal partitions, numbered 0 through 9. The
blank-subtracted absorbance value of each well is classified according to the
partition of the matrix to which it corresponds, and is reported as a signal digit. Wells
with absorbance values greater than the upper limit are reported by plus signs (+),
and wells with absorbance values less than the lower limit by minus signs (-).
(5) Cutoff report
The Cutoff report provides a qualitative report of the relative magnitude of the
absorbance values or converted concentrations on the plate.
Four types of cutoff report are supported as listed below.
a. Cutoff Constant
Ranged Cutoff Constant
The user inputs Positive and Negative values to be used as the cutoff.
For units designated "Abs", if the absorbance of a well is within the positive and
negative cutoff values, the well is scored "*". If the absorbance of a well is
greater than the positive value, the well is scored "+", and if the absorbance of a
well is below the negative value, the well is scored "-".
For units not designated "Abs", the absorbance value of each well is converted
to the concentration value using the curve fit constants of the curve fit report. If
the concentration of a well is within the positive and negative cutoff values, the
well is scored "*". If the concentration of a well is greater than the positive value,
the well is scored "+", and if the concentration of a well is below the negative
value, the well is scored "-".
Single Cutoff Constant
The user inputs Positive and Gray zone values to be used as the cutoff.
For units designated "Abs", if the absorbance of a well is within the gray zone
value of the positive cutoff value, the well is scored "*". If the absorbance of a
well is more than the gray zone value and greater than the positive value, the
well is scored "+", and if the absorbance of a well is more than the gray zone
value below the positive value, the well is scored "-".