# Typos in `Concepts in Probability and Stochastic Modeling'

The following typos appear in Concepts in Probability and Stochastic Modeling by James J. Higgins and Sallie Keller-McNulty, published in 1995 by Wadsworth.

Most of them were found by Byron Schmuland and his students at the University of Alberta.

• (page 26) In Exercise 1.4-7 (a), the correct answer is 1008.
• (page 34) In Exercise 1.5-9 (b), the correct answer is 0.325758.
• (page 42) In Exercise 1.6-11, the correct answer is 0.015625.
• (page 83) In the statement of Theorem 2.7-3, X_x should be X_1.
• (page 94) In Exercise 2.8-1 (c), the correct answers are E(C)=8.08 and STD(C)=4.593.
• (page 110) In Exercise 3.1-7, the correct answer is .217277.
• (page 128) Exercise 3.5-1 asks for P(X>2), but the answer given is for P(X>=2).
• (page 151) In Example 4.3-3, p^(2) should be P^(2).
• (page 153) In order to preserve the symmetry in the matrix P^4, and make the bottom row add up to 1, in Example 4.3-5, the bottom right-hand entry should be .347 rather than .346.
• (page 186) In Exercise 4.7-3, the solution in the text for the mean time to absorption is calculated using the cumulative distribution function F calculated in part a. Due to rounding, this is only an approximate value. The exact answer is 2.231.
• (page 187) In Exercise 4.7-5, the correct answer is 1.75676.
• (page 190/191) For the probability histograms, the left hand axis should not be labelled ``Empirical Probability". This is because it is the area of the rectangles, and not their heights, that are equal to the empirical probability. The vertical scale for the plot of the probability density function is wrong; it should be similar to the vertical scale for the two histograms.
• (page 200) In Exercise 5.1-5 (b), the correct answer is e^{-2}=.1353.
• (page 209) In Exercise 5.2-1 (a) the text give the answer 2/3 for STD(X). The correct answer is the square root of 2/9. The correct answer for part (b) is therefore the probability that X lies between zero and (2/3)+(2) sqrt(2/9), which turns out to be .96187269.
• (page 210) Exercise 5.2-5 asks you to find the density and distribution function for the random variable Y=2X+3, but the solutions are for Y=2X-3.
• (page 222) In Example 5.4-3, in the double integral at the bottom of the page, the y-variable should run from 0 to 1, not 0 to 2.
• (page 232) In Exercise 5.4-3, the given function f is not a density function. The constant 1/2 should be changed to 2.
• (page 237) On the third last line of this page, F(X) should be F(x).
• (page 241) The centre of the normal curve should be labelled mu, not x.
• (page 254) In Example 6.3-3, they refer to a Table 6, but they mean Table 5.
• (page 272) In Theorem 7.1-2 it should be P(Y=y), not P(Y>y).
• (page 281) In Table 7.3-1, the first two numbers in the u column ought to be .2012 and .8253.
• (page 292) In equation 7.5-3, that should be i to i, not i to 1.
• (page 304) In the equation at the top of the page, the term in square brackets is missing a p_S.
• (page 339) The t-values, called c(n), in Table 8.3-1 are all wrong.
• (page 379) In Exercise 10.1-2, the stated density does not integrate to 1 unless the 12 is changed to 8.
• (page 380) In Exercise 10.1-5, diagram has 2 short-circuits (i.e., as drawn components 3,4,5,6 do not matter).
• (page 391) In Exercise 10.3-1 (a), the correct answer is .3032.