1.
A 90% confidence interval has a z-score (a critical value) zc=1.6449.
E=zc×nσn≥(Ezcσ)2
n≥(0.031.6449(0.57))2
n=977
2.
A 95% confidence interval has a z-score (a critical value) zc=1.96.
E=zc×nσn≥(Ezcσ)2
n≥(0.151.96(1.2))2
n=246
3.
A 99% confidence interval has a z-score (a critical value) zc=2.5758.
E=zc×nσn≥(Ezcσ)2
n≥(0.052.5758(0.45))2
n=538
Comments
Leave a comment