NAME:
	meanerr2
 PURPOSE: (one line)
	Calculate the mean and estimated error for a set of weighted data points
 DESCRIPTION:
	This routine is adapted from Program 5-1, XFIT, from "Data Reduction
	and Error Analysis for the Physical Sciences", p. 76, by Philip R.
	Bevington, McGraw Hill.  This routine computes the weighted mean using
	Instrumental weights (w=1/sigma^2).  The final uncertainty is
	insensitive to a multiplicative constant on the weights.
 CATEGORY:
	Statistics
 CALLING SEQUENCE:
	meanerr2,x,weight,xmean,xsigma
 INPUTS:
	x      - Array of data points
	weight - array of weights for data points
 OPTIONAL INPUT PARAMETERS:
	None.
 KEYWORD PARAMETERS:
	None.
 OUTPUTS:
	xmean   - weighted mean
	xsigma  - uncertainty of xmean
 COMMON BLOCKS:
	None.
 SIDE EFFECTS:
	None.
 RESTRICTIONS:
	None.
 PROCEDURE:
 MODIFICATION HISTORY:
	Written by Marc W. Buie, Lowell Observatory, 2000/10/01
  2000/10/3, MWB, mostly WMG, it now works.