Thread: probablility...

Hello,
plz try to solve these questions.

Thanks.

(a)The probability that it will be cloudy tomorrow is 0.6 and the probability it will rain if it gets cloudy is 0.7. What is the probability that it will be cloudy and rain tomorrow?

(b)In a firm, 20 percent of the employees have accounting backgrounds, while 5 percent of the employees are executives and have accounting backgrounds. If an employee has an accounting background, what is the probability that the employee is an executive

Originally Posted by m777

Hello,
plz try to solve these questions.

Thanks.

(a)The probability that it will be cloudy tomorrow is 0.6 and the probability it will rain if it gets cloudy is 0.7. What is the probability that it will be cloudy and rain tomorrow?

if we want the probability of two events happening at the same time, we multiply the probabilities of each event together. the word "and" tips you off to this kind of probabiliy. (if it said "or" you would add the probabilities)

probability that it will be cloudy tomorrow = 0.6
probability it will rain if it gets cloudy = 0.7

probability that it will be cloudy and rain tomorrow = 0.6*0.7 = 0.42

Originally Posted by m777

(b)In a firm, 20 percent of the employees have accounting backgrounds, while 5 percent of the employees are executives and have accounting backgrounds. If an employee has an accounting background, what is the probability that the employee is an executive

now for this question, i'm not so sure (i'm not that good with probability). if it said: "what is the probability that an employee has an accounting background and is also an executive" then we'd do it as we did above. but since we are given that we have already chosen an employee, i'm not sure if we should include the first probability.

here's what i'm thinking:

20 percent of the employees have acounting backgrouds, and 5 percent have accounting backgrounds and are executives. that means, 15% have accounting backgrounds and are not executives. so for every 20 people, say, who have accounting backgrounds, 5 will also be exectives. so if that an employee has an accounting background, the probability he will be an executive is 5/20 = 0.25

Wouldn't it be 5% of the 20% ?

So then the chances are: 0.01

This is just a guess, im not really good with probability either.

Originally Posted by janvdl

Wouldn't it be 5% of the 20% ?

So then the chances are: 0.01

This is just a guess, im not really good with probability either.

i don't think so. it said "5 percent of the employees" not "5 percent of the employees that have backgrounds in accounting"