ERRORinCalc - For n questions we use the fact that...

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For n questions, we use the fact that N~Binomial(n, 0.25). Since we were using the proportion of correct answers / , ( 1) E ( ) ,and ( ) . Instead, I incorrectly used E ( ) , ( ) ( 1 ), whi X Nn pp Xp Va rX n X npVa r X n = - == = =- ch are actually for the Total # N of correct answers out of n questions. 0.3 5 0.25 If we use ,then 2.33, 0.25*0.75/ 2.33 * .1875 . . , or n = 101.79 ( n 102) to be 99% confident. .10 However, if we use N Xz n i en - =≥ , then we need P( N .35n). Approximating it by Normal distribution, ignoring continuity correction, 0.35n - 0.25n gives, z = 2.33, i.e., same as above. *0.25*0.75 Thus the answer for the incorrect problem n = actually gave the value of (1/n). If we use the continuity correction,
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This note was uploaded on 04/16/2010 for the course STAT 427 taught by Professor Staff during the Spring '08 term at Ohio State.

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