Question

P(Z < z) = 0.2578
find z

Answer 1

assuming a mean of 0 and a sd of 1 ?

Answer 2

yea

Answer 3

my first idea is to simply use a ztable to look up .2578 in its field

Answer 4

you got a ztable handy?

Answer 5

if not, you got a ti83 handy?

Answer 6

yea theres no z score showing for 0.2578

Answer 7

add .5 to it

Answer 8

and pick the closest value :)

Answer 9

but that depends on the ztable itself; different authors use different constructs ....

Answer 10

are your value all larger than .5?

Answer 11

yea

Answer 12

no, my largest vaule is .4990

Answer 13

then you should have the .2578 value in there, it wont be exact, but close

Answer 14

since the value is less than .5, we make the zscore itself negative