Question

The height of male students at PWSH is approximately normally distributed with a mean of 71 inches and standard deviation of 2.5 inches.
a) What percent of the male students are shorter than 66 inches?
b) Taller than 73.5 inches?
c) Between 66 & 73.5 inches?

Answer 1

your sexxxy

Answer 2

ok ok
i need the answer

Answer 3

please

Answer 4

do you have a TI 83 or 84 calculator?

Answer 5

no

Answer 6

alright, then wolfram alpha is the next best thing

Answer 7

for part a)

type in

normalcdf(-100,66,71,2.5)

to get the answer 0.02275

Answer 8

the normalcdf function finds the area under the normal curve

in general, you type in

normalcdf(a,b,mu,sigma)

'a' and 'b' are the endpoints of where you want to find the area

mu is the mean

sigma is the standard deviation

Answer 9

there is some formula to solve it? cause i dont know what normalcdf is

Answer 10

there is no simple formula to memorize or do this by hand

so you either have to use tables or a calculator

Answer 11

what table?

Answer 12

sometimes the book will have probability tables in it (or normal distribution tables)

Answer 13

basically it gets really complicated to do it by hand, so you need a calculator

before calculators were invented, tables were the only way to do it (in a reasonable amount of time)

Answer 14

is there something about empirical or chebyshev rules?

Answer 15

oh right, not sure why I didn't think about the empirical rule (it only works in a limited number of cases), but it looks like it will work here

Answer 16

i know the answers already, but i don't know the way to find them

Answer 17

what is the empirical rule? do you remember?

Answer 18

it is about standarts deviaton from the mean

Answer 19

99.7, 95, 68

Answer 20

yes, good, 68% of the distribution is 1 standard deviation from the mean

Answer 21

1 st deviation- 68
2-95
3-99.7

Answer 22

95% of the distribution is 2 std deviations from the mean

Answer 23

yes

Answer 24

99.7% of the distribution is 3 std deviations from the mean

Answer 25

in this case, mu = 71 and sigma = 2.5

71 - 2.5 = 68.5
71 + 2.5 = 73.5

So 68% of the distribution is between 68.5 and 73.5

Answer 26

71 - 2*2.5 = 66
71 + 2*2.5 = 76

and 95% of the distribution is between 66 and 76

Answer 27

what percentage is left over?

Answer 28

yes, you r right, i know that, but how yo solve a problem?

Answer 29

I'm getting there

Answer 30

:)

Answer 31

so 95% of the distribution is between 66 and 76

this means 100 - 95 = 5% is left over, agreed?

Answer 32

i can give you the answers

Answer 33

this 5% is distributed between the two tails

so each tail gets 5/2 = 2.5%

Answer 34

this means that roughly 2.5% of the population is shorter than 66 inches

Answer 35

i dont get it

Answer 36

what tail?

Answer 37

ok I'll try to draw a picture of the distribution