Question

seee attachment! please check my work

Answer 1

You need to use the normal distribution with the given info. When you come back, give me a shout and I'll help you with this.

Answer 2

@kropot72

Answer 3

hey i thoughtfor this kind of question u will have to use the sample size formula

Answer 4

\[S.E. = z _{\frac{ \alpha }{ 2 }}\frac{ \sigma }{ \sqrt{n} } \rightarrow n = \left[ z _{\frac{ \alpha }{ 2 }}\frac{ \sigma }{ S.E. } \right]^{2}\]

\[S.E. = 15 \text { minutes, } \sigma = 36 \text { minutes, } z _{\frac{ \alpha }{ 2 }}= 1.96... \text { \right?}\]

Answer 5

\[n=\left[ \frac{ Zc * \sigma }{ m}\right]^{2}\]

Answer 6

yup

Answer 7

m?

Answer 8

thats how i did it.. and i got all the answers.. m= E my teachers formula.. his m = margin of error

Answer 9

ahhh, makes sense now.

Answer 10

awesome! so you didn't need me...

Answer 11

no like i was wondering if i did the steps right.i got confused with this chapter cos i didnt attend class. and is it possible for u to check my answers.. if its too much its okay! :) thanks alot anyway

Answer 12

no, i don't mind. were those the answers in the bixes?

Answer 13

yupp :D thanks alott!

Answer 14

boxes

Answer 15

you did it.. not me

Answer 16

nah u helped me still.. thanks and u have helped me alot before as well

Answer 17

thanks for the kind words!

Answer 18

any more ?

Answer 19

questions

Answer 20

thats all for now.. are they all correct?

Answer 21

hold on a sec...

Answer 22

that's what I got...
Unless it comes out to be an integer, always round up to the nearest integer... Just like you did!!!
You're a pro!

Answer 23

not nearest, next

Answer 24

haha im not a pro!! so i got the answer right for al of it?

Answer 25

15 and 5, right? I got the same as you... 23 & 200

Answer 26

yup okie thanks.. okay i need help for this.. i have attached the question and my working..

Answer 27

what's the average of the data?

Answer 28

i tot the mean is 30? so the average is 30?? no?

Answer 29

I get 30.5... you stated xbar (sample mean) in your formula but you used the hypothesized population mean (mu) in your calc.

Answer 30

oh im not supposed to use the hypothesized population mean? why

Answer 31

no, the sample mean is going to follow a normal distribution with pop. mean = mu and std dev of sigma/ sqrt n.

Answer 32

okay so mean and average is a different thing? so because given is mean of it.. so i will have to find the average from the data give right?

Answer 33

it depends... what does your teacher say? typically, I would use the data because you actually measured something whereas the supposed (hypothesized) pop mean may not be based on data, but merely a target value.
But sometimes, the pop mean isn't hypothesized, it's been tested and shown to not differ significantly from that amount and then it's perfectly fine to center about that point estimate.

Answer 34

no the mean and average are the same thing, if we're talking about the same thing, i.e., sample or population.

the population mean doesn't change unless the population changes. The sample mean will vary as you take different samples.

Answer 35

why did you use 2 for the critical value? for a std normal, 95% of the data is within 1.96 std devs.

Answer 36

the empirical rule is only approximate...

Answer 37

idk thats what is given in my teachers note.. :s

Answer 38

did your teacher do any examples where the pop mean was known and the sample data provided? What value did they use?

Oh, what's in your notes? xbar or mu?

Answer 39

wow... i've never anyone literally use 2 for the # of std devs for a 95% CI. What level is this class?

Answer 40

don't get me wrong... in the grand scheme of things .04 is nothing to quiblle about. I've just never seen it done like that.

Answer 41

quibble

Answer 42

introduction to statistics.. :s idk should i use my teachers formula or use the correct 1

Answer 43

teachers... if you ever use this stuff you'll adjust very quickly.

so back to what point estimate to use for the mean... xbar or mu.
your formula shows xbar but did your teacher do any examples where both xbar and mu were available? if so, which was used?

Answer 44

i think you should use xbar. this is because the data would be pretty pointless (except for providing an n) otherwise. also, it says to construct an estimate for the true mean and they say the machine is designed to fill tires to 30 psi, not that it actually does.

Answer 45

in the example given .. he used average.. no mu

Answer 46

from his notes

Answer 47

when i teach it, I tell students that if after a hypothesis test of the mean we find there is no significant difference, that the hypothesized value is okay to use as a center for the CI. If there is a significant difference, then the sample should be used to get a point estimate for the center.

Answer 48

yeah, it only gives the sample mean.

Answer 49

okay so i guess what u said was correct.. so i have provided my corrected working on top.. it shud be correct right?

Answer 50

yep... what's 2 d.p.?

Answer 51

decimal places?

Answer 52

yup!

Answer 53

awesome! do you use a std. normal table in your classwork? Also, is this college or hs?

Answer 54

(b) Provide an interpretation of the confidence interval in (a).
If we repeatedly took a sample of 12 tires from the same population and constructed the interval in a similar manner, then 95% of such intervals will contain the true population mean

Answer 55

perfect!!!!!!!

Answer 56

its university level(undergrad first year stats course) im in canada.. im guessing ure in the states

Answer 57

yep

Answer 58

heard of Rush?

Answer 59

gold rush?

Answer 60

haha i dont think i know

Answer 61

no... the band. they're from Toronto. Just got inducted in to the rock & roll hall of fame.

Answer 62

oh haha yeahh of course

Answer 63

i tot u were talking about something else related to the states or school!

Answer 64

great, you should be proud of those guys. they are incredible... as a band and as people (imho).

Answer 65

lol

Answer 66

im guessing ure from the west coast right?

Answer 67

yeah, why?

Answer 68

lol nah just asking.. cool!

Answer 69

did something give it away?

Answer 70

what about u? mid, west or east?

Answer 71

mid! haha cold af during the winter..

Answer 72

hey for this question right.. the nul hypothesis is gonna be mu= 30 mu<30?

Answer 73

no kidding! i went to visit a friend in wisconsin in the month of november... omg! i've skied and snowboarded before but was never that cold!

Answer 74

which question?

Answer 75

lol! im from manitoba in canada.. its just too cold! flipp.. and uhh this question

Answer 76

like i wanna know if the null hypothesis is =30, <30