Method comparison / Agreement

Method comparison measures the closeness of agreement between the measured values of two methods.

• Correlation coefficient
  A correlation coefficient measures the association between two methods.
• Scatter plot
  A scatter plot shows the relationship between two methods.
• Fit Y on X
  Regression of Y on X describes the linear relationship between the methods.
• Linearity
  Linearity is the assumption that the relationship between the methods is linear.
• Residual plot
  A residual plot shows the difference between the measured values and the predicted values against the true values.
• Average bias
  Bias is a measure of a systematic measurement error, the component of measurement error that remains constant in replicate measurements on the same item. When measuring a method against a reference method using many items the average bias is an estimate of bias that is averaged over all the items.
• Difference plot (Bland-Altman plot)
  A difference plot shows the differences in measurements between two methods, and any relationship between the differences and true values.
• Fit differences
  Regression of the differences on the true value describes the relationship between the methods.
• Limits of agreement (LoA)
  Limits of agreement estimate the interval within which a proportion of the differences between measurements lie.
• Mountain plot (folded CDF plot)
  A mountain plot shows the distribution of the differences between two methods. It is a complementary plot to the difference plot.
• Agreement measures for binary and semi-quantitative data
  Agreement measures summarize the similarity of the results of two binary or semi-quantitative methods.
• Agreement plot
  An agreement plot shows the agreement between two binary or semi-quantitative methods.