Question

Average:1332
Standard diviation:725
(a) What proportion of tax returns show a refund greater than $2,000?
(b) What proportion of the tax returns show that the taxpayer owes money to the government?
(c) What proportion of the tax returns show a refund between $100 and $700?

Answer 1

lol ... i need the practice :)

Answer 2

z = (2000 - 1332)/725 = .9214

Answer 3

what can you find me for a z of .92?

Answer 4

.8212?

Answer 5

i agree. .8212 is everything less than our zscore; we want whats greater than it sooo:

1 - .8212 should be good

Answer 6

the total is 1 and we want whats left over

Answer 7

.1788 for a

Answer 8

good

Answer 9

so when the refund is less than 0 they owe right?

Answer 10

z=(0 - 1332)/725 = ?

Answer 11

-1.8372

Answer 12

z = -1.84 is what i get as well

Answer 13

so what value can you get me for a z of -1.84?

Answer 14

.9671?

Answer 15

thats a bit high; but the table is measureing zs that are to the right of the mean; so subtract .5 from it to begin with

Answer 16

OR, 1 - .9671 should do it since that is what it would be if we flipped the chart

Answer 17

ok so .0329

Answer 18

.0329 is good

Answer 19

the trick is in figuring out the ztables info and where we need to be in relation to it

Answer 20

next one:

$100 and $700

z1 = (100-1332)/725

z2 = (700-1332)/725

Answer 21

both of these are to the left of the mean so they are -z values

Answer 22

-1.6993 and -.8717

Answer 23

those look good, and the table is gonna give us the ... "wrong" values for both of them so we need to take the table and subtract it FROM 1

Answer 24

then we can determine the distance between z2 and z1 by subtracting the "corrected" values

Answer 25

.0455 and .1922?

Answer 26

.0475 and .1922 is what i get

Answer 27

so it would be .1467?

Answer 28

.1447 if you adjust for your typo ;)

Answer 29

or is that my typo?

Answer 30

-1.70 the round off right?

Answer 31

http://www.wolframalpha.com/input/?i=z%3D-1.699

Answer 32

oh it is .1476

Answer 33

.0447

Answer 34

I didn't round to -1.70 earlier

Answer 35

.1475 is in the ball park

Answer 36

thank you for helping me

Answer 37

yep, thanks for the practice :)