- CFA Exams
- CFA Exam: Level I 2021
- Study Session 2. Quantitative Methods (1)
- Reading 8. Probability Concepts
- Subject 1. Introduction

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**CFA Practice Question**

Suppose a traffic light cycles through green for 180 seconds, then yellow for 10 seconds, and then red for 110 seconds. Find the probability that at a certain time the light is green. Find the odds in favor of the light being green.

B. 0.60; 3:5

C. 0.60; 3:2

A. 0.01; 3:5

B. 0.60; 3:5

C. 0.60; 3:2

Correct Answer: C

Odds: 180:(110 + 10) = 3:2

p = 180 / (180 + 110 + 10) = 0.6

Odds: 180:(110 + 10) = 3:2

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**User Contributed Comments**
7

User |
Comment |
---|---|

Renaud1807 |
Can someone explain the odds? And how to find it with the BAII? |

Beret |
Odds of a to b means probability E = a/(a+b) = 0.60, Here a = 180 and b = 10 + 110 |

Bobokoko |
prob of success (0.6)/prob of failure (0.40)= 1.5/1 or to lose the decimal, 3:2 |

stitcher |
Prob of Green P(G) = 180/300 =.6 consider binomial with P(G) as success 1-P =.4 Odds for are P(G)/P(G c) = 6/4 3/2 3:2 |

Sanghamitra |
thanks all for making it so clear! |

abhishekcj |
why not 3:5 |

s214111 |
60/1-60=60/40=3/2 or 3:2 |