Practice Exam 2 Solutions

# Practice Exam 2 Solutions - Practice Exam 2(Solutions...

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Practice Exam 2 (Solutions) ECO221 1. Pdf of distribution is f(x)=1/10 for x = 1, 2, 3, …10. Find a mean for this distribution. a) 10; b) 5.5; c) 6; d) 5. 2. What is the variance for this distribution? a) 99/12 b) 100/12 c) 111/12 d) 11 3. Assume, f(x)= 1/20 is a pdf for a continuous. What is the probability of 0 < x < 10 ? 4. Suppose, variance for X is σ2, what is the variance of (2X+7)? 5. 4. The standard normal distribution is a normal distribution whose 6. A typist makes on average an error every 500 words. Typical page contains 300 words. What is the probability that there will be no more than two errors in 5 pages? a) 10% b) 50% c) 42% d) 37% Comment: You can use Poisson distribution with λ=5*300*(1/300)=3; P(X ≤ 2)=e -3 +3e -3 +(3 2 /2)e -3 =42%

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