Statistical Power - People.stat.sfu.ca

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Example: effect of people camping near nests on time spent by eagles with their nestlings.! Treatments: 100m and 500m; effect size: 20%;  α = 0.1; power = 0.2! Test: 2-tailed t-test for independent samples! Results: null hypothesis not rejected; (t = 0.54, df = 52, p = 0.59, observed effect = 4.5%, se = 4.1)! ! Problem: eagle nesting behaviour changes rapidly as nestlings mature (not accounted for)! Power and Research Design
• Change to crossover (paired) design! • Treatment and control are both applied to the same experimental unit (nest)! • Eliminates variability due to nestling age.! • Null hypothesis rejected (t = 2.19, 26 df, p = 0.038).! • Eagle behaviour change when people camp near their nests.! • Pooled sd in CRD: 29.8; sd for paired design: 10.7, even though sample size is half.! Power and Research Design
Page 1 and 2: STATISTICAL POWER ANALYSIS IN WILDL
Page 3 and 4: !Interrelated components: target po
Page 5 and 6: !Effect: magnitude of response, ori
Page 7 and 8: • Set a meaningful effect size,
Page 9: Typical constraints:! • Maximum n
Page 13 and 14: Power is calculated using sample si
Page 15 and 16: Confidence Intervals and Power
Page 17 and 18: Points To Remember:! • Hypothesis

Statistical Power - People.stat.sfu.ca

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