Question

The accompanying table shows the scores on a classroom test. What is the population standard deviation
x: 100, 95, 90, 80, 75, 72, 70
f: 7, 2, 10, 4, 2, 3, 4

Answer 1

ooh statistics.....dont remember this but tiere's a formula for Standard Deviation...google it lol

Answer 2

f stands for frequency, so that's the number of x' of that particular value that occurred.
So x = 100 occurred 7 times in the population.
x = 95 occurred twice. And so on.

Find the mean of your population is the first step.
That means summing over all the scores of the class and dividing by the class size.

Answer 3

\[\sum_{n=1}^{3}i^(n-1)\]

Answer 4

that should read i^(n-1)

Answer 5

what's that?

Answer 6

sum?

Answer 7

What is that sum for formula for?

Answer 8

the top part means you do the formula on the right 3 times using n=1 n=2 n=3 and then add up all those values

Answer 9

but the i is raised to the n-1

Answer 10

What's the formula represent? Is this a different problem? I thought you were asking about standard deviation.

Answer 11

yeah its a different problem i figured out the other one ill use my calculator

Answer 12

So what's the sum asking you to do? You want to find an explicit formula for the sum?

Answer 13

no you need to find the sum of all those terms

Answer 14

I have a feeling you wrote the problem wrong. As it is, it makes no sense.
Unless the teacher just wants you to write: i^(0) + i^(1) + i^(2). That's the sum.

Answer 15

yeah u do i^1+i^2+i^3 and add them up

Answer 16

you start with 1 because thats what n=

Answer 17

You raise it to (n-1). So when n = 1, n-1 is 0. So the first power is 0. The next power increased by 1, so it's 1.

Answer 18

nev ermind its fine..can you look at my probability question

Answer 19

no i gotta go

Answer 20

if you post it on here, someone will be sure to help. there's a lot of people on right now

Answer 21

okk

Answer 22

good luck