Context : The determination of meteoroid mass indices is central to flux measurements and evolutionary studies of meteoroid populations .
However , different authors use different approaches to fit observed data , making results difficult to reproduce and the resulting uncertainties difficult to justify .
The real , physical , uncertainties are usually an order of magnitude higher than the reported values .

Aims : We aim to develop a fully automated method that will measure meteoroid mass indices and associated uncertainty .
We validate our method on large radar and optical datasets and compare results to obtain a best estimate of the true meteoroid mass index .

Methods : Using MultiNest , a Bayesian inference tool that calculates the evidence and explores the parameter space , we search for the best fit of cumulative number vs. mass distributions in a four-dimensional space of variables ( a,b,X _ { 1 } ,X _ { 2 } ) .
We explore biases in meteor echo distributions using optical meteor data as a calibration dataset to establish the systematic offset in measured mass index values .

Results : Our best estimate for the average de-biased mass index for the sporadic meteoroid complex , as measured by radar appropriate to the mass range 10 ^ { -3 } > \mathrm { m } > 10 ^ { -5 } g , was s = -2.10 \pm 0.08 .
Optical data in the 10 ^ { -1 } > \mathrm { m } > 10 ^ { -3 } g range , with the shower meteors removed , produced s = -2.08 \pm 0.08 .
We find the mass index used by is substantially larger than we measure in the 10 ^ { -4 } < m < 10 ^ { -1 } g range .

Conclusions :