Estimating the detection limit using a probit fit
Fit a probit regression model to estimate the limit of detection.
- Select a cell in the dataset.
-
On the Analyse-it ribbon tab, in the
Statistical Analyses group, click Fit Model, and then click
Probit.
The analysis task pane opens.
- In the Y drop-down list, select the binary response variable.
- In the Event drop-down list, select the positive outcome.
- In the X drop-down list, select the level variable.
- Next to the X drop-down list, click the drop-down menu, and then in the Transform drop-down list, select Log 10
- In the Plot drop-down list, select Scaled - X against Y.
- Clear the Individual check box, and select the Aggregate check box.
- On the Analyse-it ribbon tab, in the Fit Model group, click Predict, and then click X given Probability.
- On the analysis task pane, in the Fit panel, in the Predict X given Probability edit box, type 0.95
- Click Calculate.
On the analysis report, in the Predict X for Given
Probability section, the predicted level at 0.95 probability is the
limit of detection.
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