
Well, this value here is just a point. It's mu, which is what we already know,

the mean clock score, 37.72 in our last example, plus 1.96. It doesn't really

make sense to add a z score, so this value is not an interval and it doesn't

even make sense. Here, we're getting a little closer because now we have an

interval. But as I said before, it doesn't make sense to just subtract a z score

because this is the number of standard deviations away from the mean, so we want

to find the value along the xaxis for this interval. This one looks more

promising. We have our sample mean. And we subtract 1.96 standard deviations,

and since the standard deviation is sigma divided by root n that would be this

value here, and then if we add 1.96 standard deviations that would give this

value here. And that is our confidence interval. So, we found the answer. But

let's explore this one anyway. This one we can't even figure out what it is

because we don't know this population mean after the intervention. So, we're not

able to compute this. If you selected this one, then you were pretty close. So,

good job.