I have taken a special interest on sample size calculations for
randomized controlled trials. I believe that the sophistication of
the sample size methods commonly used has not kept pace with the
complexity of the experimental designs most often employed in
practice by economists (or at least that is my take after reviewing
research proposals for different funding bodies). This led me to
write (jointly with Brendon McConnell) a practitioner's guide to
more complex methods to compute the required sample.
Going
beyond simple sample size calculations: a practitioner's guide
(jointly with Brendon McConnell). IFS
Working Paper 15/17
In this paper, we compile available methods for sample size
calculations for continuous and binary outcomes with and without
covariates, for both clustered and non-clustered RCTs. Formulae for
panel data and for unbalanced designs (where there are different
numbers of treatment and control observations) are also provided.
The paper includes three extensions: (1) methods to optimize the
sample when costs constraints are binding; (2) simulation methods to
compute the power of a complex design; and (3) methods to consider
in the sample size calculation adjustments for multiple testing. The
paper is provided together with spreadsheets and STATA code to
implement the methods discussed.
Click here to view accompanying sample
size calculators for this paper.
Please, come back for material that we will be adding in the
future!