Sampling philosophy
Sambrook Research strongly believes that better results to policy questions are achieved by a focused qualitative research approach. Key policy issues usually emerge after the first few days of interviewing, and subsequent data reinforces the initial picture and adds weight to the findings.
The 90% information threshold
Experience has shown that knowledge gathered by in-depth, qualitative interview techniques rapidly rises up the learning curve.
Quite modest samples therefore result in rapidly diminishing returns in terms of new information.
Most (if not all) of the major strategic issues will have been clearly identified and prioritised once the research project has crossed the ‘90% information threshold’. Any new emerging trends usually involve only issues of minor importance.
Cells of 10-15 interviews yield consistent, reliable information
The bar chart below (using anonymised data from a past study) shows that the order of importance of the buying issues is almost identical for the small sample of 10 interviews and the large sample of 200.
A minimum of 10-15 interviews per 'cell' of similar target organisations is sufficient to obtain a clear understanding of the primary strategy issues.
Some minor changes of position occur as the sample size changes, but importantly for both the large and small sample sizes
- primary issues remain at the top
- secondary issues in the middle
- minor issues remain at the bottom