Question

the 90% confidence interval for the mean one-way commuting time in NY is 37.8 14 years ago

Answer 1

the mean itself is what; 38.3 maybe?

Answer 2

z = (x-mean)/sd

whats the ztable value for 45% from the mean?

or 5% on the tail depending on how yout tables are setup

Answer 3

if i read it right, z for 90% interval is like 1.645 maybe

Answer 4

yea

Answer 5

sd = (x-mean)/z they give 2 xs so lets pick say 37.8

we know the mean is 38.3

the differecne between them is .5

sd = .5/1.645 then; .3039 perhaps?

now the zscore for a 95% from the table is: 1.96

solve for a new "x"

1.96 = (x-38.3)/.3039

1.96(.3039)+38.3 = value to the right of the mean

Answer 6

38.9 is what I kind of get

means that we are .6 from the mean 38.3-.6 = 37.7 maybe?

Answer 7

or with any luck :: crosses fingers::

CI = mean +- z(sd)
= 38.3 +- 1.96(.3039)
= 37.7 , 38.9

depending on how accurate you need to get