Arithmetic and Geometric Means for Outcomes

Arithmetic values are calculated with the arithmetic mean and the geometric values are calculated with the geometric mean. "Arithmetic" and "geometric" refer to the way the average value is calculated. The main difference between arithmetic and geometric values is the way outliers in the data are handled.

Arithmetic and geometric means are applied to the following outcomes:

• Charge
• Cost
• LOS

For more information, refer to the QualityAdvisor Methodologies Guide.

Arithmetic Mean

Arithmetic mean calculations are a simple aggregation of the outcomes for all patients in an identified population divided by the total number of patients. As a result, the extreme outliers can have a significant impact on the resulting mean value.

Geometric Mean

The geometric mean applies a logarithmic function to the data that constrains the effect of outliers on the total. The geometric mean in QualityAdvisor analyses is typically less than the number returned by the arithmetic mean because of the natural lower bound of zero for cost and LOS data and the reduction in the effect of the highest values.