In contrast the Fisher test is, as its name states, exact as long as the experimental procedure keeps the row and column totals fixed, and it can therefore be used regardless of the sample characteristics.

Similarly, a detailed description of sample characteristics, including gender, ethnicity, and attrition rates is necessary for determining generalizability.

The descriptions of sample characteristics are often inconsistent and leave out essential information necessary to evaluate if generalization is appropriate or not.

If Wahis are deployed on a public website, the sample characteristics are unlikely to be representative of the general population - the data collected are generally used for qualitative analysis and developing hypotheses rather than reaching definitive conclusions.

- Compared to classical test theory, IRT parameter estimates are not as confounded by sample characteristics.

The statistical analyses required to estimate the genetic and environmental components of variance depend on the sample characteristics.

Differences in sample characteristics may explain some part of it (for instance in Ipswich the action samples contained a higher proportion of heavily dependent people who went straight into institutions after their referral to the psychogeriatric service).

External validity was called into question concerning sample characteristics.

Whatever the reason for the discrepancy - varied definitions, survey methods and sample characteristics could all be involved - the gap is too large for me to take either figure as definitive.