Artikkel om konfidensintervaller og styrkeberegning

  • Artikkel om konfidensintervaller og styrkeberegning

Artikkelen er publisert i Clinical Chemistry. Les mer her.



Reliable estimates of within-person biological variation and reference change values are of great importance when interpreting test results, monitoring patients and setting quality specifications. Little has been published regarding what experimental design is optimal to achieve the best estimates of within-person biological variation.


Expected confidence intervals were calculated for different balanced designs for a two-level nested variance analysis model with varying analytical imprecision. We also simulated datasets based on the model to calculate the power of different study designs for detection of within-person biological variation.


The reliability of an estimate for biological variation and a study’s power is very much influenced by the study design and by the ratio between analytical imprecision and within-person biological variation. For a fixed number of measurements, it is preferable to have a high number of samples from each individual. Shortcomings in analytical imprecision can be controlled by increasing the number of replicates.


The design of an experiment to estimate biological variation should take into account the analytical imprecision of the method, and focus on obtaining the highest possible reliability. Estimates of biological variation should always be reported with confidence intervals.

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