# Using repeated measurements

When repeated measurements (replicates) are made for each subject, it is inefficient to estimate average bias and limits of agreement using only the first measurement, rather than all measurements.

If replicates are available, it is sensible to use the mean of the replicates to estimate average bias. However, when estimating the limits of agreement, the reduction in the standard deviation due to averaging of the measurements must be considered and adjusted for if necessary.

The mean difference estimate is 6.0, which indicates that the Mini Wright meter reads on average 6.0 l/min higher than the Wright meter. The confidence interval is narrower because the measurement error was reduced by using the mean of the replicates.

The limits of agreement estimate an interval of -67.8 to 79.8, which indicates that the Mini Wright meter may measure as much as 67.8 l/min below and 79.8 l/min above the large meter. This would be unacceptable for clinical purposes. Again, the confidence intervals are narrower due to the use of more measurements.

- Tutorials
- Distribution tutorial
- Correlation / PCA tutorial
- Compare groups means tutorial
- Association in 2-way contingency tables tutorial
- Simple linear regression tutorial
- Bland-Altman method comparison tutorial
- Plotting the relationship between methods
- Estimating the average bias and the limits of agreement
- Understanding the importance of repeatability
- Using repeated measurements
- Dealing with a relationship between difference and magnitude of measurement
- Transforming the measurements to remove a relationship between differences and magnitude
- Estimating regression based limits of agreement when transformation is not enough
- Estimating nonparametric limits of agreement in non-normally distributed data
- Verifying the precision of a measurement procedure against a performance claim and estimating the bias (CLSI EP15-A3)
- Pareto charts tutorial
- Process control charts tutorial
- Process capability tutorial

Published 16-Nov-2017

Version 4.92