Can I combine pilot data with main study data?
Pilot data is often a small scale data set used to assess study feasibility prior to a larger main study. The two data sets may be combined provided the sampling strategy is the same and there are no changes over time e.g. in precision of equipment or questions in a test manual.
The two articles below advocate pooling pilot and study data given the above constraints and give further thoughts on using pilot studies.
Altman D, Burton N, Cuthill I, Festing M, Hutton J and Playle L (2006) Why do a pilot study? Published findings of NC3Rs Experimental Design Working Group report. This article also gives further references on pilot studies.
Thabane L, Ma J, Chu R, Cheng J, Ismaila A, Rios LP, Robson R, Thabane M, Giangregorio L and Goldsmith CH (2010) A tutorial on pilot studies: the what, why and how. BMC Medical Research Methodology 10:1.