Question

In a survey of 1000 randomly chosen adults, 605 said that they used email. Calculate a 90% confidence
interval for the proportion of adults in the whole population who use email.

Answer 1

605/1000 is our "mean" as i recall

Answer 2

have to review a little to make sure what to do next :)

Answer 3

z*sqrt(pq/n)

Answer 4

the zscore for 90% is ...

Answer 5

\[\frac{605}{1000}\pm z*\sqrt{\frac{605}{1000}\frac{395}{1000}\frac{1}{1000}}\]

Answer 6

Is it OK if you can find out some more background info on this matter? Like, maybe a site to explain this more?

Answer 7

http://www.stat.wmich.edu/s160/book/node47.html

this is what refreshed it for me

Answer 8

Thanks for it... So, from the last step you wrote, how do you continue?

Answer 9

you determine the zscore for 90% and plug it into the rest to determine your interval

Answer 10

So, how do you determine the zscore? With a table... or?

Answer 11

table, yes; or ti83

Answer 12

I don't have a graphic calc... Would you use the Modulus Function table... or?

Answer 13

oy this thing is slooowwww this morning

Answer 14

this measures the z from the mean itself; so we want .4500 from the mean so that the total area from the mean is 90%

Answer 15

.4500 in the feild is there in the middle; it rests neatly between 1.64 and 1.65

1.645 should be the zscore then

Answer 16

\[.605\pm 1.645\sqrt{.605*.305*.001}\]

Answer 17

the ;ower and upper limits of that stuff define the interval

Answer 18

Hmm.. Ok... I don't have this table in my statistics book. Do you think they'll give it me in the exam?

Answer 19

lol, i doubt it.

the table should be on the back cover

Answer 20

or in a leaflet; its called a ztable

Answer 21

Hmmm... I hope they do! ztable? What's the difference between a ztable and a modulus function table?

Answer 22

depends on what a modulus function table is :)

Answer 23

I mean a normal distribution table...?

Answer 24

http://www.google.com/search?q=normal+distribution+table&hl=en&prmd=imvns&tbm=isch&tbo=u&source=univ&sa=X&ei=7J9DT6FwkZO3B4urkM0K&ved=0CDEQsAQ&biw=1280&bih=923

yes

Answer 25

But... the z table you first gave looks different than the normal distribution table?

Answer 26

there are a few ways that it is written up depending on how the authors like to display it

the main difference is in what they measure from.

Answer 27

in my book; they measure from the mean itself; in other books they measure from a tail