<p>Students in one section of English210 received 31%A\'s,40%B\'s,20%C\'s,4%D\'s

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<p>Students in one section of English210 received 31%A's,40%B's,20%C's,4%D's and 5%F's.<br />(a)Using the common scale A=4,B=3,C=2,D=1,F=0,take X to be the grade of a randomly chosen English210 student.Use the definitions of the mean and standard deviation for discrete random variables to find the mean&#160;&#956; and the&#160;standard deviation&#160;&#963; of grades in this course. &#160;(b)English210 is a large course as we take the grades of simple random sample(SRS) of 50 students to be independent of each other.If x is the average of these 50 grades,what are the mean and standard deviation of x? &#160;(c)What is the probability P(X&gt;=3) that a randomly chosen English210 student gets a B or better? What is the approximate probability P(x&gt;=3) that the grade for 50 randomly chosen English210 students is B or better?&#160;</p>

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