EXAM 1-A - STAT 400 Fall 2011 Version A Name BD1 Th 2:30...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon
STAT 400 Fall 2011 Name ANSWERS . Version A BD1 BD2 BD3 BD4 Th 2:30 We 4:00 We 4:00 Th 2:30 317 DKH 165 Noyes 143 Altgeld 328 Armory Srijan Sengupta Srijan Sengupta Robert Eisinger Robert Eisinger Exam 1 Please circle your discussion section. Be sure to show all your work; your partial credit might depend on it. No credit will be given without supporting work. The exam is closed book and closed notes. You are allowed to use a calculator and one 8½" x 11" sheet with notes. Page 1 2 3 4 5 6 7 Total Earned / 70
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
1. Alex sells Statistics Made Easy videos over the phone to finance his college education. Suppose 30% of all calls result in a sale. Assume that the outcome of each call is independent of the others. a) (3) What is the probability that Alex makes his first sale on the fourth call? No sale No sale No sale Sale (0.70) (0.70) (0.70) (0.30) = 0.1029 . b) (5) What is the probability that Alex makes his first sale on an even-numbered call? P(even) = P(2) + P(4) + P(6) + … = + + + 5 3 1 70 . 0 0.30 70 . 0 0.30 70 . 0 30 . 0 = 17 7 49 . 0 1 1 21 . 0 49 . 0 21 . 0 70 . 0 21 . 0 0 0 2 = - = = = = n n k k 0.4117647 . OR P(even) = + + + 5 3 1 70 . 0 0.30 70 . 0 0.30 70 . 0 30 . 0 P(odd) = + + + 4 2 0 70 . 0 0.30 70 . 0 0.30 70 . 0 30 . 0 P(even) = 0.70 P(odd), P(odd) = 7 10 P(even). 1 = P(odd) + P(even) = 7 17 P(even). P(even) = 17 7 0.4117647 . c) (3) What is the probability that Alex makes his third sale on the eighth call? [ 7 calls: 2 S’s & 5 F’s ] S ( ) ( ) [ ] 70 . 0 30 . 0 2 7 5 2 C 0.30 0.0953 .
Background image of page 2
1. (continued) d) (3) If Alex makes 10 calls, what is the probability that he makes exactly 4 sales? Let X = the number of sales made during 10 phone calls. The outcome of each call is independent of the others Binomial distribution, n = 10, p = 0.30. Need P( X = 4) = ? k n k p p k C n k X - - = = ) 1 ( ) P( P( X = 4) = 6 4 ) 70 0 ( ) 30 0 ( 4 10 . . C = 0.20012 . OR Using Cumulative Binomial Probabilities: P( X = 4) = P( X 4) – P( X 3) = CDF @ 4 – CDF @ 3 = 0.850 – 0.650 = 0.200 . e)
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 4
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/15/2012 for the course STAT 400 taught by Professor Kim during the Spring '08 term at University of Illinois, Urbana Champaign.

Page1 / 11

EXAM 1-A - STAT 400 Fall 2011 Version A Name BD1 Th 2:30...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online