[1] He studied Mathematics at the University of Cambridge[1] and completed his PhD in Statistics at Imperial College London,[1] supervised by Sir David Cox.
[2] Firth is known for his development of a general method[3] for reducing the bias of maximum likelihood estimation in parametric statistical models.
Together with a PhD student, Renée de Menezes, Firth also established the generality of the method of quasi variances, a device for summarizing economically the estimated effects of a categorical predictor variable in a statistical model.
[7][8] Firth developed (in collaboration with John Curtice) a new statistical approach to the design and analysis of election-day exit polls for UK General Elections.
The new methods have been used at UK General Elections since 2005 to produce the widely broadcast close-of-polls forecast of seats in the House of Commons.