Question

This question is killing me! Stats alpha sign question!

Answer 1

What's your full question?

Answer 2

its on its way sorry its an attachment \

Answer 3

that's ok, take your time

Answer 4

I'll be right back

Answer 5

No problem thank you for even looking at the question, im so stumped =)

Answer 6

ok I'm back now @Tomfoolery1

Answer 7

let me have a look at the problem

Answer 8

you mentioned alpha, but alpha isn't shown in this problem

you might be mixing up sigma with alpha?

anyways, since there are 40 students, this means n = 40. Agreed? or no?

Answer 9

Yes! 40 yea i might have been mixed XD sorry

Answer 10

that's ok

Answer 11

what is the value of xbar (ie the sample mean) ?

Answer 12

59.4?

Answer 13

yes so \[\LARGE \bar{x} = 59.4\]

Answer 14

sigma is given to be \[\LARGE \sigma = 10.5\]

Answer 15

since sigma is known/given, this means we use the standard normal distribution (not the T distribution)

Answer 16

we only use the T distribution if sigma is not known or if n is smaller than 30

Answer 17

do you see where it says "click here to view page 1 of the standard normal distribution table" ?

Answer 18

yes i see it!

Answer 19

click the link and show me what pops up

Answer 20

ok

Answer 21

page 2 looks the same as this as well?

Answer 22

Yea its the positive side

Answer 23

we have a 99% confidence interval, which means that we have something like this set up

http://sherrytowers.com/wp-content/uploads/2014/09/normal.png

instead of 95%, picture that as 99%

in each tail, we have 0.5% = 0.005

since 100% - 99% = 1% and we cut that 1% in half

Answer 24

look through the table you're given

locate inside the table a value that is close to 0.005

Answer 25

i found .5199

Answer 26

do you see where it says 0.0505 ? its on page 1

Answer 27

oohh yes i do!

Answer 28

what is the corresponding z score?

Answer 29

-1.645!

Answer 30

very good, so the critical z value we'll use is z = 1.645

Answer 31

The lower bound L of the confidence interval is

\[\LARGE L = \bar{x} - z*\frac{\sigma}{\sqrt{n}}\]
\[\LARGE L = 59.4 - 1.645*\frac{10.5}{\sqrt{40}}\]
\[\LARGE L = ??\]

Answer 32

do you see what I'm asking?