00:01
We're looking at a study on marijuana use, and let's start by writing down the information we've been given.
00:08
There were 145 positive tests, but 30 of them are false.
00:15
There were 151 negative tests, and how many of these are false? there are four false.
00:24
I think that says four.
00:26
A little bit small.
00:27
Yep, four.
00:29
Four false.
00:30
Okay, so we need to answer some questions here.
00:37
First of all, how many subjects were there? so part a, this one is easy.
00:42
We know how many tests have been done.
00:43
All we have to do is add them up.
00:45
So 296 tests have been completed in total.
00:51
And that's how many subjects there were.
00:55
B, how many of them did not use marijuana? so if we start with the positive tests, 145 tested positive, but 30 didn't actually use marijuana...