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