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),whiX NnppXpVarXnXnpVarXn=-====-ch are actually for the Total # N of correct answers out of n questions.0.350.25If we use ,then 2.33,0.25*0.75/2.33*.1875. ., or n = 101.79 (n102) to be 99% confident..10However, if we use NXznien-=≥, then we need P(N.35n).Approximating it by Normal distribution, ignoring continuity correction,0.35n - 0.25ngives, z =2.33, i.e., same as above.*0.25*0.75Thus the answer for the incorrect problemn≤=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.