Question

You're going to use your TI-83 graphing calculator to compute the area between
values of 7 and 9 for a distribution whose mean is 8 and whose standard deviation
is 2. You would enter:
A. normalcdf(7,9,8,2)
B. normalpdf(7,9,8,2)
C. invNorm(8,7,9)
D. normalcdf(8,2,7,9)
E. normalpdf(8,2,7,9)

Answer 1

@jim_thompson5910

Answer 2

think back to the template

normalcdf(a,b,mu,sigma)

a = lower bound
b = upper bound
mu = mean
sigma = standard deviation

Answer 3

the first two numbers (a & b) are the bounds

the next two are the mean and std dev

Answer 4

if you leave out the mean and std dev, it assumes you're dealing with the standard normal distribution. So it uses the default values of mu = 0 and sigma = 1

Answer 5

so which one is it

Answer 6

ok hold on

Answer 7

a?

Answer 8

its either a or b

Answer 9

do you see the difference in the two?

Answer 10

yes

Answer 11

but i dont know exactly how they r different

Answer 12

the pdf is for single points on the curve

the cdf is for areas under the curve

Answer 13

you use cdf more I think

Answer 14

oh so cdf is area

Answer 15

so it is a

Answer 16

ok cool thnxs

Answer 17

correct

Answer 18

can i ask the next one on this thread ?

Answer 19

A normal probability plot is used to:
A. determine the area between two normal curve values.
B. test a distribution for normalcy.
C. help find the z-score corresponding to an area under a normal curve.
D. convert raw data to standardized scores.
E. compare raw data to z-scores.

Answer 20

its fine either way

Answer 21

there may be other uses for a probability plot, but the main use is to see if you're dealing with a normal distribution

http://www.itl.nist.gov/div898/handbook/eda/section3/normprpl.htm

if the transformed points all line on or close to a straight line, then the distribution is considered to be normal. Otherwise, it is not a normal distribution and it may be distributed in some other way.

Answer 22

so its B

Answer 23

correct

Answer 24

cool ty one more?

Answer 25

ok

Answer 26

Consider normally distributed data with a mean of 35 and a standard deviation of
2. If there are 350 values between 31 and 33, how many values are there in the
distribution?
A. 2525
B. 2550
C. 2575
D. 2600
E. 2625

Answer 27

first calculate the area under the curve from 31 to 33

Answer 28

oh ok ithink i know how to do that

Answer 29

yep use normalcdf

Answer 30

i got 0???

Answer 31

nvm its .135

Answer 32

normalcdf(31,33,35,2) is what you should type in

Answer 33

yes, so 0.135*x = 350, solve for x

Answer 34

2592

Answer 35

I'm getting the same

Answer 36

so will it be 2600?

Answer 37

one sec

Answer 38

k

Answer 39

I'm getting 0.135905122 for the result on the normal cdf, so,


0.135905122*x = 350

x = 350/0.135905122

x = 2,575.32604253134

Answer 40

ok

Answer 41

ty SOOOO much, will u be here in the future?

Answer 42

yeah I should be