2 Direct Comparisons with Scatter Plots & Regression Modeling

Module 7 Comparing Measurement Systems

Lesson M7-02

Duration: 17 minutes

Direct Comparisons with Scatter Plots & Regression Modeling

Lesson 2 illustrates direct comparisons of two measurement systems using scatter plots with a 45-degree line.  Bias/Differences between the measurement systems may be easily observed based on the location of the paired observations vs. the 45-degree line.  Linearity may be assessed by comparing the 45-degree line to a fitted regression line.  We discuss how a value observed on one measurement system may be used to predict the value that would be observed on the other measurement system.  It may be a constant adjustment or variable adjustment depending on whether the bias/offset depends on the measured value. Prediction intervals are introduced which may be used to quantify the uncertainty in predicted values.