Question

pic posted!! just check my answer please!!

Answer 1

@blurbendy @pgpilot326

Answer 2

@mary.rojas

Answer 3

Whats 80 percent of the highest score?

Answer 4

@gypsy1274 help?

Answer 5

@phi help?

Answer 6

use a z table to find how many std dev 80% is above the average

Answer 7

sorry my z table is confusing so its not that confusing

Answer 8

my answer is D. 580 but im NOT SURE!

Answer 9

*SO ITS NOT THAT HELPFUL

Answer 10

this table
http://www.sjsu.edu/faculty/gerstman/EpiInfo/z-table.htm
says s.d. is 0.84

so you are 100 pts * 0.84 = 84 pts above 500
584

to the nearest multiple of ten, that is 580

Answer 11

yay :)

Answer 12

:)

Answer 13

also to what statistical quantity does "sigma" refer to?

Answer 14

So you need to find the z-score associated with 80%, meaning 80% of the scores lie below that value. Looking at the table, we look inside at the probabilities and look for .3000 or the value closest to it. This is because .5 + .3 = .8 or 80%.
A z-score of .84 comes closest (.2995) so now I have to convert that to an SAT score.
\[z=0.84=\frac{ x-\mu }{ \sigma }\]
we want to solve this for x using the info in the problem.
Thus \[x=z \times \sigma+\mu=\left( 0.84 \right)\left( ? \right)\left( 100 \right)+500=584\]

Answer 15

yeah its ok, @phi said my answer(580) was correct :)

Answer 16

but my next question is:
what statistical quantity does "sigma" refer to?

Answer 17

it's the standard deviation
the z-score formula is a conversion, like yards to feet.

Answer 18

ok so STANDARD DEVIATION

Answer 19

im going to submit it ok

Answer 20

Imagine you have 4 feet and want to convert it to yards. you take the feet and divide by 3 because there are 3 feet per yard. Right?
z-scores are exactly the same, except sigma or std dev is our yardstick.
Suppose we are 6 units away from the mean and our std dev is 2 units. How many std devs away from the mean are we? This is exactly what the z-score is asking.
So we are 3 std devs away from the mean and our z-score is just that... 3.
Hope that helps.

Answer 21

The + or - is telling us if we're above or below the mean, resp.

Answer 22

oh.. yeah that kinda makes sense

Answer 23

The right-hand "tail" of the standard normal curve can be defined as the part of it that lies at least two standard deviations to the right of the mean.

According to the Empirical Rule, approximately what percentage of the area under the whole curve is in the right-hand tail? Round your answer to the nearest tenth.

Answer 24

☼☼NEW QUESTION☼☼

Answer 25

need to do this one fast!

Answer 26

look at the table with z = 2.00. subtract this from .5 and you'll have your answer.

Answer 27

subtract 2-.5?

Answer 28

no... if z = 2.00, the area from the mean to z=2 is .4772. the area in the tail is .5 - .4772 = .0228. Rounded to the nearest tenth, that's 0.

Answer 29

wut? I thought it was 2+ 0.5 so I was gonna submit 2.5 ...

Answer 30

im not sure if ur right on this

Answer 31

@mary.rojas

Answer 32

@phi

Answer 33

@pgpilot326 r u sure!!!?? :( :(

Answer 34

not 2.5. the z-scores are on the outside of the table. they represent the number of std devs from the mean. the values inside the table are the probabilities (same as the area under the curve). You don't combine the two, you relate the two.

Answer 35

no I mean are u sure it's .228... cuz that's 0!!

Answer 36

or 0.0228 same thing :p

Answer 37

oh, sorry. did I put the decimal in the wrong spot? No, I did it correctly. The area in the tail is 0.0228. If this is rounded to the nearest tenth it would be 0 right?

Answer 38

yea.. I just feel hesitant cuz 0 would be the answer.. which feels weird to me, but ill submit it anyways

Answer 39

ok really quick- my next q.!

Answer 40

yeah, I know what you mean. It seems like an odd way to ask the question.

Answer 41

Empirical rule. Within 1 std dev you expect 68%, within 2 you expect 95%. This is within 1 std dev (plus or minus 1), so 0.68.

Answer 42

whew! id already submitted that

Answer 43

☼next one☼

Answer 44

is this D?

Answer 45

or wait whats the right answer?

Answer 46

I think I know it. what is it

Answer 47

Didn't we already do this one?

Answer 48

yea but I think its asking for something else

Answer 49

@music101 open a new post because this post is too long!!! lol!

Answer 50

ok.