00:01
We have been given some sample data.
00:02
The sample size, n, is 120.
00:06
Out of these, 42 scores more than 550 on the math sat.
00:13
Part a, we want a point estimate for the population proportion who scores more than 550.
00:19
So a point estimate is basically your best guess for the parameter based on the information you have been given.
00:27
So what is your best guess for proportion of all students who meet this criteria? well, it's the sample proportion, 42 out of 120, which i will calculate 0 .35.
00:49
Next, we want to make a confidence interval for the population proportion.
00:54
What formula should you be using? so this is the ti series of graphical calculators, the kind of standard, and the formula, the function you want to use on your ti -84 or ti -85, is called 1 -prop -z -int.
01:11
So what this means is it's a single sample, so one sample, and therefore one sample proportion, and it's an interval based on the z -scores.
01:24
So that's the critical value it's using.
01:26
I'll write out the formula your calculator will be using as well.
01:30
P -hat, it's point estimate, plus and minus the margin of error, z root p -hat, 1 minus p -hat over n.
01:38
So you can absolutely work this out yourself if you find z, but this is a function where if you put in n and x and the level of confidence, c equals 0 .98, it will give you your interval...