Table 2 The estimated sample sizes required to detect a housing effect using between-subject t tests (with alpha = 0.05, and power = 0.8).

From: Welfare-improving enrichments greatly reduce hens’ startle responses, despite little change in judgment bias

Subjects

Judgment bias

Startle amplitude

All hens (not controlling for personality)

164 per group

5 per group

Exploratory hens

85 per group

3 per group

Non-exploratory hens

N/A

4 per group

  1. Estimates are based on the mean differences between housing treatments, pooled standard deviations and the resulting effect sizes (from the first tests run, before the housing switch; see Supporting Material), and were calculated using online calculators, e.g. http://www.sample-size.net/sample-size-means/. The “N/A” for Non-exploratory hens reflects the lack of predicted direction of the effect, thence lack of validity as an affect indicator, for judgement bias in this sub-group.
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