00:01
So we're asked to show the steps using a ti -84 plus on a calculator for these problems.
00:08
So i'm going to do that and the first thing you're going to want to do is go to second, bars, and then you're going to go to number two, normal cdf.
00:25
Now in my calculator when i go to normal cdf i have this screen.
00:29
You may not have this screen depending on your calculator.
00:37
Different versions of these graphing calculators have different things.
00:42
If you have a parenthesis you're still going to go in this order.
00:45
It will be lower comma, upper comma, mu, and sigma.
00:50
So what we're going to do is we're going to enter in for a, what's the probability of a randomly selected student in the city will read more than 94 words a minute.
01:00
So our lower is 94 because we're going to be more than that.
01:03
And our upper, you can set that to, you know, i just put one and as many zeros as i can until i run out of space.
01:12
So you could do one e to the 99th power but you can also do this.
01:18
Our mu, they gave us a mean of 90 words a minute so we're going to put that mu here and our sigma of 10 goes here.
01:25
And then we hit enter.
01:27
So for a, i'm going to put a here.
01:35
So for a we get a probability of .3446.
01:40
Select the correct choice below and fill in the answer box with your choice.
01:46
So of those options go ahead and choose a.
01:51
And a says if 100 different students were chosen from this population we would expect 34 .46 is what we should fill in to read more than 94 words per minute.
02:01
Now for part b, the only thing we're going to change is our sigma.
02:08
So we still are finding the probability of reading more than 40 or 94 words a minute.
02:14
But in part b we have a random sample of 14 second grade students.
02:19
So when we get to, when we go back in, the only thing we're going to change is we're going to take 10 and divide it by the square root of 14.
02:27
To get our standard error is what we call that.
02:29
And that obviously is going to change our probability.
02:33
Because now our probability is going to be .0672.
02:38
And of our options we'll go with option c.
02:41
If 100 independent samples of 14 students were chosen from this population we would expect samples to have a sample mean reading rate.
02:48
We would expect in this case 6 .72 samples to have a mean reading rate of more than 94 words per minute...