09_08ans - STAT 400 Fall 2011 Examples for Binomial...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
STAT 400 Examples for 09/08/2011 Fall 2011 Binomial Distribution : 1. The number of trials, n , is fixed. 2. Each trial has two possible outcomes: “success” and “failure”. 3. The probability of “success”, p , is the same from trial to trial. 4. The trials are independent. 5. X = number of "successes" in n independent trials. Then ( ) ( ) k n k k n k p p k C n p p k n k - - = - - = = 1 1 P ) ( X , where k = 0, 1, … , n . E ( X ) = n p Var ( X ) = n p ( 1 p ) SD ( X ) = ( ) p p n - 1 1. Bart Simpson takes a multiple choice exam in his Statistics 101 class. The exam has 15 questions, each has 5 possible answers, only one of which is correct. Bart did not study for the exam, so he guesses independently on every question. Let X denote the number of questions that Bart gets right. a) Is it appropriate to use Binomial model for this problem? Yes . Binomial, n = 15, p = 1 / 5 = 0.20. b) What is the expected number of questions that Bart would get right? E ( X ) = n p = 15 0.20 = 3 . c) What is the probability that Bart answers exactly 3 questions correctly? P
Background image of page 1

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

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 11/07/2011 for the course STAT 400 taught by Professor Kim during the Fall '08 term at University of Illinois, Urbana Champaign.

Page1 / 5

09_08ans - STAT 400 Fall 2011 Examples for Binomial...

This preview shows document pages 1 - 2. Sign up to view the full document.

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