Math experts also scuba right?

[wcl]

You're reading way to much into it. 50% say they work, not 50% say they ONLY work.

Besides, if they were independent, you'd have 110%, so they can't possibly be independent. It's much simpler than you seem to think

Well, I didn't want to infer the absence or presence of the "only", on general principles.

Indeed, however, I didn't even bother to look at the numbers to see if the percentages given might indicate which choices are pertinent (D'oh!).

Old reflex, make the student think clearly in formulating the question before proceeding. Half the time, that heads straight for the answer immediately with no further discussion.

Ultimately, my goal was to show the path without walking it hand-in-hand.

Two cardinal rules of probability & statistics:
1. The question is way more important than the answer, and extreme clarity there is crucial.
2. From that point onwards, ultimately it is just simple, careful counting (as you demonstrate).

Cheers,
Walter

 

[Walter]

My mistake, I read the 19% as a separate group. The 19% is the information I said was missing. I humbly apologize, you are correct, 72% is the right answer. I was wrong.

 

[nkw5]

Thank you all for your input. My mind is at ease now. I accept 72% as the answer. I am also pleased to know there are some math experts on the board.

 

[divad]

It's a trick question. The answer has already been given to you.

Yeah, why isn't the answer 100 % since there is a 0% chance of picking some one not in one of the 3 groups?

 

[jonnythan]

Yeah, why isn't the answer 100 % since there is a 0% chance of picking some one not in one of the 3 groups?

Because there is a fourth group in the age group.. they are the "lazy butts"

 

[divad]

Because there is a fourth group in the age group.. they are the "lazy butts"

I am an idiot.