β and b

maartenbuis

TS Contributor
#2
It depends on how these symbols are defined. There are conventions on what these symbols mean, but these differ by sub-discipline, and even within sub-disciplines they are not consistently used. So the only thing you can do is read carefully what the definition is in each text you read, and expect these definitions to differ across texts (even if they are written by the same author).
 

noetsi

Fortran must die
#3
Given that notation is not standardized in statistics the first refers most commonly to the value of the unknown population parameter, and the second to the estimate of that value from your sample.
 

hlsmith

Omega Contributor
#4
The first may represent a matrix of Betas from a model and the second a value from the matrix, perhaps?? Though, as noted, usages can be mixed up and not consistent.