<< Chapter < Page Chapter >> Page >

(See Exercise 1 from "Problems on Distribution and Density Functions", m-file npr07_01.m ). The class { C j : 1 j 10 } is a partition. Random variable X has values { 1 , 3 , 2 , 3 , 4 , 2 , 1 , 3 , 5 , 2 } on C 1 through C 10 , respectively, with probabilities 0.08, 0.13, 0.06, 0.09, 0.14, 0.11, 0.12, 0.07, 0.11, 0.09.Determine E [ X ] .

% file npr07_01.m % Data for Exercise 1 from "Problems on Distribution and Density Functions" T = [1 3 2 3 4 2 1 3 5 2]; pc = 0.01*[ 8 13 6 9 14 11 12 7 11 9]; disp('Data are in T and pc')npr07_01 Data are in T and pcEX = T*pc' EX = 2.7000[X,PX] = csort(T,pc); % Alternate using X, PXex = X*PX' ex = 2.7000
Got questions? Get instant answers now!

(See Exercise 2 from "Problems on Distribution and Density Functions", m-file npr07_02.m ). A store has eight items for sale. The prices are $3.50, $5.00, $3.50, $7.50, $5.00, $5.00, $3.50, and $7.50, respectively.A customer comes in. She purchases one of the items with probabilities 0.10, 0.15, 0.15, 0.20, 0.10 0.05, 0.10 0.15. Therandom variable expressing the amount of her purchase may be written

X = 3 . 5 I C 1 + 5 . 0 I C 2 + 3 . 5 I C 3 + 7 . 5 I C 4 + 5 . 0 I C 5 + 5 . 0 I C 6 + 3 . 5 I C 7 + 7 . 5 I C 8

Determine the expection E [ X ] of the value of her purchase.

% file npr07_02.m % Data for Exercise 2 from "Problems on Distribution and Density Functions" T = [3.5 5.0 3.5 7.5 5.0 5.0 3.5 7.5]; pc = 0.01*[10 15 15 20 10 5 10 15]; disp('Data are in T, pc')npr07_02 Data are in T, pcEX = T*pc' EX = 5.3500[X,PX] = csort(T,pc);ex = X*PX' ex = 5.3500
Got questions? Get instant answers now!

(See Exercise 12 from "Problems on Random Variables and Probabilities", and Exercise 3 from "Problems on Distribution and Density Functions," m-file npr06_12.m ). The class { A , B , C , D } has minterm probabilities

p m = 0 . 001 * [ 5 7 6 8 9 14 22 33 21 32 50 75 86 129 201 302 ]

Determine the mathematical expection for the random variable X = I A + I B + I C + I D , which counts the number of the events which occur on a trial.

% file npr06_12.m % Data for Exercise 12 from "Problems on Random Variables and Probabilities" pm = 0.001*[5 7 6 8 9 14 22 33 21 32 50 75 86 129 201 302]; c = [1 1 1 1 0]; disp('Minterm probabilities in pm, coefficients in c')npr06_12 Minterm probabilities in pm, coefficients in ccanonic Enter row vector of coefficients cEnter row vector of minterm probabilities pm Use row matrices X and PX for calculationsCall for XDBN to view the distribution EX = X*PX'EX = 2.9890 T = sum(mintable(4));[x,px] = csort(T,pm);ex = x*px ex = 2.9890
Got questions? Get instant answers now!

(See Exercise 5 from "Problems on Distribution and Density Functions"). In a thunderstorm in a national park there are 127 lightning strikes. Experience shows that the probability of of a lightning strike starting a fire is about0.0083. Determine the expected number of fires.

X binomial (127, 0.0083). E [ X ] = 127 · 0 . 0083 = 1 . 0541

Got questions? Get instant answers now!

(See Exercise 8 from "Problems on Distribution and Density Functions"). Two coins are flipped twenty times. Let X be the number of matches (both heads or both tails). Determine E [ X ] .

X binomial (20, 1/2). E [ X ] = 20 · 0 . 5 = 10 .

Got questions? Get instant answers now!

(See Exercise 12 from "Problems on Distribution and Density Functions"). A residential College plans to raise money by selling “chances” on a board. Fifty chances are sold. A player pays $10 to play; he or she wins $30with probability p = 0 . 2 . The profit to the College is

X = 50 · 10 - 30 N , where N is the number of winners

Determine the expected profit E [ X ] .

N binomial (50, 0.2). E [ N ] = 50 · 0 . 2 = 10 . E [ X ] = 500 - 30 E [ N ] = 200 .

Got questions? Get instant answers now!

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Applied probability. OpenStax CNX. Aug 31, 2009 Download for free at http://cnx.org/content/col10708/1.6
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Applied probability' conversation and receive update notifications?

Ask