HW3Solution

# HW3Solution - Introduction to Geostatistics Homework 3 Due...

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Introduction to Geostatistics Homework 3 – Due 25 February, 2008 Section 2.4 – Page 111 1. Determine whether each of the following random variables is discrete or continuous a. The number of heads in 100 tosses of a coin. A n s Discrete - The number can only be an integer, so there are gaps between the potential outcomes. b. The length of a rod randomly chosen from a day’s production. Ans Continuous – If you (reasonably) assume that the measurement contains many significant digits, then there are no gaps between outcomes. c The final exam score of a randomly chosen student from last semester’s engineering statistics class. Ans Discrete – Normally, it’s discrete because test grades will be rounded to the nearest integer. Rarely would grades be given in a continuous fashion. d. The age of a randomly chosen Colorado School of Mines student. Ans Continuous – This really depends on how you record the age (i.e. of you are rounding up/down). But like the example in class, the outcomes are really continuous. For example, Mr. A is 25 yrs 10 months 15 days 21 hrs 12 mins 43.123345678 seconds. e. The age that randomly chosen Colorado School of Mines student will be on his or her next birthday. Ans Discrete – At the exact moment of the anniversary of one’s birth, he/she is exactly n years old, so this RV only contains integers. 2. The following table presents the probability mass function of the number of defects X in a randomly chosen printed-circuit board. x0123 p ( x ) 0 . 50 . 30 . 10 . 1 a Find P(X < 2) Ans P(X < 2) = P(X = 0) + P(X = 1) = 0.5 + 0.3 = 0.8 b. Find P(X >= 1) Ans P(X >= 1) = P(X = 1) + P(X = 2) + P(X =3) = 0.3 + 0.1 + 0.1 = 0.5 c Find x μ

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Ans = x P(X = x) = 0 * P(X=0) + 1 * P(X=1) + 2 * P(X=2) + 3*P(X = 3) = 0 * 0.5 + 1 * 0.3 + 2 * 0.1 + 3 * 0.1 = 0.8 d Find Ans = ( x - ) 2 P(x) = (0-0.8) 2 * 0.5 + (1-0.8) 2 * 0.3+ (2-0.8) 2 * 0.1 + (3-0.8) 2 * 0.1 = 0.96 3. A chemical supply company ships a certain solvent in 10-gallon drums. Let X represent the number of drums ordered by a randomly chosen customer.
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HW3Solution - Introduction to Geostatistics Homework 3 Due...

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