00:01
For this problem to begin, we're told to assume that the marginal frequencies are correct, but that the values in the individual cells are not.
00:10
So if we have that the marginal frequencies are correct, what that means is that the total across each row and across each column is correct, but the individual values are not.
00:21
So in order to continue on with answering this question, one thing that we're going to need to do is find those marginal frequencies.
00:28
So let's see here, 60 plus 30 plus 10, that's going to be 100.
00:33
40 plus 40 plus 20, 80 plus 20 is 100.
00:37
20 plus 30 is 50, so 20 plus 30 plus 50 is 100.
00:42
And then for our column, 60 plus 40 would be 100, and then we add 20, so that's 120.
00:49
30 plus 30 is 60, add 40 gives us 100.
00:53
Then 10 plus 20 is 30, 30 plus 50 is 80.
00:59
And we have a grand total of 300.
01:02
So now that we have those marginal frequencies, we get rid of everything else.
01:07
We're assuming that the individual cell entries are unknown.
01:11
We're asked, if age and phone preference were independent, how many people age 66 or older would prefer a mobile phone? so we'd have that the number of individuals age 66 plus, and would prefer...
01:34
Okay, one second here.
01:36
I'm assuming that when they say would prefer a mobile phone that's counting both the smartphone and the other mobile phone...