Why smaller error obtained by error weighted?

Newbie
1

I just take an example to illuminate my confusions.
There are six experiment results on the branching fraction of Ds+ -> tau+ nu from PDG 2018,

(1). 4.83 +/- 0.65 +/- 0.26 from BESIII

(2). 5.70 +/- 0.21 +0.31(-0.30) from BELLE

(3). 4.96 +/- 0.37 +/- 0.57 from BABAR

(4). 6.42 +/-0.81 +/- 0.18 from CLEO

(5). 5.52 +/-0.57 +/- 0.21 from CLEO

(6). 5.30+/-0.47+/-0.22 from CLEO
The PDG combined the above six experiment results with error weighted method, the average branching fraction is 5.48 +/- 0.23.

My confusion is that why this error weighted method makes the final error(0.23) so small ?

And What I really want to know is, for one analysis, if we combined the results from different tag modes, whether we can use the same method to obtain the final statistic error and systematic error?

Thank you very much!

2

Search for “average” in:
2018 Review of Particle Physics -> Introduction

You could also have a look at:
2018 Review of Particle Physics -> Probability
2018 Review of Particle Physics -> Statistics

1 Like
3

Thank you for your information. I will look at them carefully.