62/3335–8FE Reference Handbook 10.4 · Engineering Economics · Risk

Handbook formula

Expected Value of Alternatives

Under risk with given probabilities, pick the alternative with the best expected NPW (or AW). Variance is a second tie-breaker if the problem asks for risk attitude.

Probability of outcome i
Payoff (NPW) of outcome i

Step-by-step solved example

Project: 0.3 chance of NPW=$40k, 0.7 of $10k. E[NPW]?

E[X]12345An
Two (or more) possible NPW outcomes weighted by probability.
  1. 1. Compute

    0.3×40+0.7×10=12+7=19 k$.

  2. 2. Decision

    Compare with do-nothing (0) or other E[NPW].

Answer: E[NPW]=$19,000

10 practice questions

0/10 correct

1.Probabilities of a complete set of outcomes must sum to

2.A risk-neutral decision maker maximizes

3.E[aX+b] =

4.If two outcomes 20 and 0 are equally likely, E =

5.Variance is

6.A sure $10 vs 50% of $20: risk-neutral is

7.Decision trees fold back by

8.p=0.2, x=100; p=0.8, x=−10; E =

9.If probabilities are unknown, FE problems may use

10.Correlation between two projects matters when