Stat 21 Quiz _3 Key

X px wins3 153604167 loses1 15364167

This preview shows page 1. Sign up to view the full content.

This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: a commuter leaves her house at 8am each morning of a 5‐day work week, and each commute time is independent from all the others, what is the chance she will arrive to work by 8:40am on 3 of those days? True. P = .27 K=3 N=5 5! / 3! (5-3)! * .27^3 (1-.27)^2 = .105 Stat 21 Quiz #3 October 12, 2011 Name______________________________________________ Section # ___________________________________________ VERSION D 1. X is a random variable defined as: x ‐1 0 1 P(x) .20 .35 .45 A) Draw the cumulative distribution function (cdf) for X. B) Evaluate: i) P(X ≥ 1.8) = 0 ii) P(X ≤ ‐2.3) = 0 iii) P(X ≥ 0.5) = 0.45 D) Calculate: i) E(X) = 0.25 X ‐1 0 1 E(x) = Var(X) = P(X=x) 0.2 0.35 0.45 0.25 0.5875 ii) Var(X) = 0.5875 x ‐ u ‐1.25 ‐0.25 0.75 (x ‐ u)^2 1.5625 0.0625 0.5625 (x ‐ u)^2 * P(X=x) 0.3125 0.021875 0.253125 Stat 21 Quiz #3 October 12, 2011 2. Francie is playing a dice game with another GSI. In the game, she rolls a dice two times. If the second roll is bigger than the first, she wins \$3. If the second roll is less than first, she loses \$1. If the second roll is equal to the first roll she wins no money, but does not lose money. A) Create a probability model for the amount of money that Francie wins in the dice game. x P(x) Wins \$3 15/36 = 0.4167 Loses \$1 15/36 = .4167 No wins or losses (if two rolls are the same) 6/36 = .167 B) Draw a cumulative distribution function...
View Full Document

This document was uploaded on 03/12/2014 for the course STAT 21 at Berkeley.

Ask a homework question - tutors are online