Question

Consider a normal distribution that has N(55,7) (that is, a mean of 55 and a
standard deviation of 7). To the nearest integer, the percentile rank of a value of 50
in this distribution is:
A. 76
B. 48
C. 43
D. 24
E. 71

Answer 1

@jim_thompson5910

Answer 2

is 50 above or below the mean?

Answer 3

it is below @jim_thompson5910

Answer 4

so what percentiles can you eliminate based on that

Answer 5

b,c,d

Answer 6

why those 3?

Answer 7

because they would only qualify if it was above the mean

Answer 8

no, you might be mixing up things

Answer 9

oh

Answer 10

if you're in the 71th percentile, then that means 71% of the population is below you

Answer 11

oh ok ty

Answer 12

so I eleminate Aand E

Answer 13

you can only be in the 71st percentile if you are above the mean

Answer 14

yes

Answer 15

sorry lol so how do i eliminate the rest?

Answer 16

as for the rest, I think we have to use a calculator

do you have one?

Answer 17

yes

Answer 18

what kind?

Answer 19

ti84

Answer 20

ok go into the stats menu

hit 2nd, then the vars key

Answer 21

look for normalcdf

Answer 22

ok

Answer 23

found it

Answer 24

the normal cdf function has this basic template

normalcdf(a,b,mu,sigma)

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

Answer 25

the lower bound will be some very big negative number, like -99 or something

the upper bound is 50

Answer 26

ok

Answer 27

tell me what you get

Answer 28

do press enter?

Answer 29

yeah once everything is in

Answer 30

ok i did and all it did was put things in parenthesis

Answer 31

you should have this typed in (I'm not showing the result just so you can get the result on your own)

Answer 32

after that's all typed in, hit enter

Answer 33

oh ok one sec and thnxs

Answer 34

notice how it fits the template

normalcdf(a,b,mu,sigma)

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

Answer 35

ok one sec and then after i press enter than what do i do?

Answer 36

ok i got it whats next?

Answer 37

what result did you get

Answer 38

exatly what i saw on your calcualtor

Answer 39

oh -.76

Answer 40

hmm that's not what I'm getting

Answer 41

you typed in exactly what I did right?

Answer 42

ok one sec

Answer 43

oh one sec

Answer 44

i put 99 not -99

Answer 45

.23

Answer 46

hmm interesting it didn't throw an error

Answer 47

you should get something like 0.2375251875

Answer 48

multiply that by 100 to get 23.7525262%

roughly 23.7525262% of the population is below this score

Answer 49

that rounds to 24% so its the 24th percentile

Answer 50

ahh ok cool ty

Answer 51

np

Answer 52

could u plz help me with 2 more?

Answer 53

sure

Answer 54

ty SOOO MUCH!

Answer 55

ill start a new thread

Answer 56

ok