Question

500 juniors at Central High School took the Act last year> The scores were normally distributed with a mean of 24 and a standard deviation of 4.
A)What percentage of scores are lower than 12?
B)Approximately how many juniors score high than 30

Answer 1

can you help me @vishweshshrimali5

Answer 2

Sorry statistics is not my strong point

Answer 3

do you know someone who can help

Answer 4

can you help @OOOPS

Answer 5

@ganeshie8 well he can help you or provide the names of the users.

Answer 6

@ganeshie8

Answer 7

@No.name

Answer 8

anyone!!!!

Answer 9

familiar with calculating zscores ?

Answer 10

hw do you do that

Answer 11

\[\large \text{Zscore = } \dfrac{\text{observation} - \text{mean}}{\text{standard deviation}}\]

Answer 12

`A)What percentage of scores are lower than 12?`

start by finding the Zscore for the observation 12

Answer 13

so zscore=500-24/12

Answer 14

sorry it is 12=500-24/4

Answer 15

i got 119 though

Answer 16

nope, you're given :
mean = 24
standard deviation = 4

Zscore for observation 12 :

\[\large \text{Zscore = } \dfrac{\text{12} - \text{24}}{\text{4}} = -3 \]

Answer 17

oh

Answer 18

look up the area for a Zscore of -3 in your ztable

Answer 19

0.0010

Answer 20

http://www.stat.ufl.edu/~athienit/Tables/Ztable.pdf

Answer 21

I am seeing 0.0013 ?

Answer 22

sorry i did -3.1 by accident its 0.0013

Answer 23

Yes ! multiply it by 100 to get the percent :

0.0013 is the probability, which is same as 0.0013x100 = 0.13 %

Answer 24

So 0.13% of the juniors will score less than 12 in ACT.

Answer 25

we're done with partA!
see if you can try partB

Answer 26

so 30-24/4=1.5

Answer 27

so 93.32%

Answer 28

thankyou

Answer 29

!!!!!

Answer 30

small blunder

Answer 31

Ztable always gives you the probability for "<"

Answer 32

B)Approximately how many juniors score `high` than 30

since you want to know higher than 30, you need to subtract the area from 100% :

percent students higher than 30 = 100% - 93.32%
= 6.68%

Answer 33

whats 6.68% of 500 ?