Transcript infmortpower2.ppt

Infant Mortality and Economics
Need for power curve
We did not reject H: slope is zero
• If we can show our statistical method – simple
linear regression, one-sided test for slope at
level .05 – has power at reasonable levels of
the slope, then our ‘failure to reject’ actually
supports the Hypothesis that the slope is
really zero
What’s a big slope?
• Infant mortality ranges 2 to 12 (deaths/k
births)
• Income ranges $50k-$100k
• Big slope ∆y/∆x = 10/50k = .0002
• Modest slope ∆y/∆x = 2/50k = .00004
High power?
Low power?
What’s a big slope?
• Infant mortality ranges 2 to 12 (deaths/k
births)
• Income ranges $50k-$100k
• Big slope ∆y/∆x = 10/50k = .0002
• Modest slope ∆y/∆x = 2/50k = .00004