<PRE><B>Question 557127</B>
Students at a high school know that January means preparation for midterms. About 11 out of 20 students usually increase their amount of studying in preparations for midterms. What is the probability that less than 40% of a 45 person sample actually increases its studying habits? 
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mean = 11/20 = 0.55

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z(0.40) = (0.40-0.55)/sqrt[0.55*0.45/45] = -2.0226
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P(p &lt; 0.4) = P(z &lt; -2.0226) = 0.0216
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Cheers,
Stan H.
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