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Unformatted text preview: 8 of 13 1.3 Confidence interval for p Relationship of n and E 200 400 600 800 1000 0.0 0.2 0.4 0.6 0.8 1.0 Relationship of sample size and margin of error (95% CL) ( p ^ = 0.5 29 sample size: n margin of error: E E = 1.96 ( 0.5 29 ( 0.5 29 n Example 5 . You have been hired by the Clear Optical company 4 to design a study to estimate the proportion of the US population who wear corrective lenses. The desired margin of error is 1% (at the 95% confidence level). What is the minimum sample size you should use? (Assume we dont know p yet.) R: alpha = 1- 0.95 R: E = 0.01 R: p . hat = 0.5 R: q . hat = 1- p . hat R: z = qnorm(1- alpha/2) R: z [ 1 ] 1.9600 R: n = p . hat * q . hat * ( z/E) 2 R: n [ 1 ] 9603.6 Thus, to attain the desired margin of error (at the 95% confidence level), a random sample of 9604 people should be used. CONFIDENCE INTERVAL BELT GRAPHS 4 Because you did so well in your statistics class....
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This note was uploaded on 02/10/2012 for the course MAT 1670 taught by Professor Tanbakuchi during the Spring '11 term at University of Florida.
- Spring '11