# The Computation of Mean Values

For the **UBV** and **uvby** systems we have computed weighted mean
values.

### The procedure has two steps:

**The first step**
- consists of a simple weighted mean, the weight being the number of
measurement to the 2/3 power. This exponent gives slightly less weight
to observations with a number of measurement much larger than usual.
- This is also the unique step for stars with two sources of measurements
only.
**The second step**
- uses the differences between each measurement and the mean
value computed on the first step. The measurements are now weighted
according to the distance to the mean. This procedure gives a lower weight
to discrepant values and the computed mean value is closer to that defined by the
majority of sources.

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mermio@scsun.unige.ch

Last update: 16 March 1996