I need help trying to better understand question b and c please

[jcooper015]

50/130= .3846 or 38.46%

 

[jcooper015]

Let's actually do what I suggested:

Here it is:
View attachment 13341
Those are all the people interested in stocks. You are asked,

If an investment client’s main investment interest is stocks, what is the probability that he or she is a banker?​

So, among these people (those interested in stocks), what is the probability of being a banker?

This is what conditional probability is.

50/130=.3846 or 38.46%

 

[jcooper015]

(50/331)/(130/331)=.3846 or 38.46
Its the intersection divided by P(A) right?
It also gives the same answer as 50/130=.3846 or 38.46%

 

[JeffM]

50/130= .3846 or 38.46%

Yes. At last.

 

[Dr.Peterson]

I see you have now used both approaches (the single column, and the formula) and found the same answer. Do you understand now? (And do you see that we have been giving you two different easy ways to think about it?) Some people find the meaning easiest to work with, others like formulas; together, they can provide actual understanding of the concept, which is more valuable than either alone.

 

[jcooper015]

Thanks I understand now.

 

[HallsofIvy]

"A. What is the probability that an investment client is a doctor?"
According to your table there are a total of 331 investment clients and 72 of them are doctors. 72/331= 0.217 to three significant figures.

"B. If an investment client’s main investment interest is stocks, what is the probability that he or she is a banker?"
According to your table there are 130 clients whose main interest is stocks and 50 of them are bankers. 50/130= 0.385 to three significant figures.

"C. What is the probability than an investment client’s main interest is not in bonds?"
According to your table there are 331 clients and 108 of them have a main interest in bonds so 331- 108= 223 clients whose main interest is NOT in bonds. 223/331= 0.674 to three significant figures.