Question

PlZ HELP EXPLAIN!

Answer 1

z with a small 0.05 under it means it wants to know the value of k such that

P(Z < k) = 0.05

Answer 2

ok?

Answer 3

do you know what I mean?

Answer 4

not really no.

Answer 5

remember how earlier we were finding areas under the curve?

Answer 6

yah

Answer 7

well now, we have an area (0.05) and we want to find the boundary marker k that gives us that area of 0.05

Answer 8

we basically want to find which value of k gives us an area of 0.05 where the area is to the left of k

Answer 9

so i look up 0.05 on the z score table?

Answer 10

actually, sry to the right of k

so you would be looking at 1 - 0.05 = 0.95

so look in an inverse normal table for 0.95

Answer 11

ok one sec i'll look for that

Answer 12

alright

Answer 13

0.8289?

Answer 14

no

Answer 15

it's probably better if we use a calculator, do you want to do it that way?

Answer 16

oh i see where you went wrong

Answer 17

you're looking at the wrong table

Answer 18

that table will give you the area under the curve for a given z score (it will give it to the left of that z-score)

Answer 19

?

Answer 20

if you wanted to find the area to the left of z = 0.95, then you would get an area of roughly 0.8289

Answer 21

so i need this table?

Answer 22

that's not what you want though

Answer 23

that's basically the same table (just using different numbers for z)

Answer 24

how do you do it on a calculator?

Answer 25

if you are using wolfram alpha, then you would type this in

invnorm(0.95)

to get this

http://www.wolframalpha.com/input/?i=invnorm%280.95%29

Answer 26

notice in the first row where it says "left tail" it shows

P(Z < 1.645) = 0.95

Answer 27

so that's how they got 1.645

Answer 28

ahhh ok i get that now. lol ok i'll try that with my homework question now

Answer 29

thank you! that defiantly helped!

Answer 30

alright, glad it's making sense now

Answer 31

@jim_thompson5910 UGH now it says i'm wrong!
It was the same problem as on the example except it was
x=120 n=300 and 99%

i got the the rest right till i got here and it said this was what it was supposed to be.

Answer 32

0.1/2 isn't 0.005

0.1/2 = 0.05

Answer 33

oh is it a 99% CI?

Answer 34

i know that but they said it was 0.005

Answer 35

ok then it should be 0.01/2 = 0.005

Answer 36

how?!

Answer 37

because you have a significance level of alpha = 1 - 0.99 = 0.01

then you divide that in half to get the area in each tail

Answer 38

btw it should be 2.576 not 2.575

Answer 39

http://www.wolframalpha.com/input/?i=invnorm%280.995%29

Answer 40

THIS IS SO CONFUSING! ok well it gave me a new problem so i'll try that.

Answer 41

alright

Answer 42

ok so this is the new problem

Answer 43

i did p with this thing^ over it =x/n=60/300=0.2
am i right so far?

Answer 44

yep

Answer 45

btw p^ is sometimes called "p-hat"

Answer 46

ok good so now i have np-hat(1-p-hat)>_10 =300(0.2)(1-0.2)>_10 =48>_10

Answer 47

you can use p for short

p-hat is definitely cumbersome

Answer 48

but looks good to me

Answer 49

yes it is lol & ok.
so 48 is greater then 10 so a=0.1 right?

Answer 50

correct, so a/2 = 0.05

Answer 51

so i do 1-0.05 & get 0.95 which =1.645?

Answer 52

good

Answer 53

ok now i think i can do the rest cause that part was the part i get stuck on. one sec.

Answer 54

alright

Answer 55

YAY i got it!! dang that was a pain!

Answer 56

that's great, well the harder they are, the more likely you'll remember them (and learn from it)

Answer 57

thx! again for the millionth time.

Answer 58

you're welcome