Mean difference is a measure of the average discrepancy between two sets of paired measurements. It is calculated by determining the difference between each pair of observations and then averaging those differences across all observations. Mean difference provides an indication of systematic bias between two measurement methods, showing whether one method consistently produces higher or lower values than the other. A mean difference close to zero suggests little systematic bias, whereas larger positive or negative values indicate greater disagreement between methods (1).

In the context of concurrent validity, mean difference can be used to assess the agreement between an IMU and a force plate when measuring countermovement jump (CMJ) height. A small mean difference indicates that, on average, the IMU produces jump height values similar to those obtained from the force plate, while a larger mean difference suggests that the IMU systematically overestimates or underestimates jump height relative to the criterion measure.

📋References

1. Doğan NÖ. Bland-Altman analysis: A paradigm to understand correlation and agreement. Turkish Journal of Emergency Medicine [Internet]. 2018 Dec 1;18(4):139–41. Available from: https://www.sciencedirect.com/science/article/pii/S2452247318302462

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