MATH 032 Midterm: math32_2009s_exam1
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Instructions: answer all questions, without the use of notes, books or calculators. Partial credit will be awarded for correct work, unless otherwise speci ed. The total number of points is 80: (25 points: 5 each) only nal answers to this problem are going to be graded. (a) the following is the histogram of a data set. The probability that he must stop at the rst signal is 0. 4. The probability that he must stop at the second signal is 0. 5. Spring semester 2009: (25 points total) the lifetime in hours of a certain kind of radio tube is a random variable having a probability density function f (x) = . 0, x 100, k x2 , x > 100. (a) (6 points) find the value of k. (b) (6 points) write down an expression to calculate the expected lifetime of this kind of tubes.
