Question

Can someone help me with normal distribution?

Answer 1

whats the question

Answer 2

It's about finding a percentile of IQ scores between 20-34 year olds. Mean is 110, standard deviation is 25.

Answer 3

@Gabetheawesome2

Answer 4

Ok what do you want us to do

Answer 5

Find the 80th percentile of the IQ scores distribution of 20 to 34 year olds.

Answer 6

what grade are you In? I might not know this

Answer 7

Im in 6th what grad did you learn this. I am sorry If I cant help

Answer 8

teach me the basics, and I might b able to help

Answer 9

Its ok Im hard to teach any way

Answer 10

@TheEdwardsFamily @dan815 @SithsAndGiggles

Answer 11

what Is that?

Answer 12

hm...is this the same type of question we did yesterday?

Answer 13

No this is something new

Answer 14

oh ok. one sec

Answer 15

It's the same idea I just don't know the percentile stuff.

Answer 16

Here's a site that shows you how to do it: https://statistics.laerd.com/statistical-guides/normal-distribution-calculations.php

Answer 17

I got that stuff, but thanks anyways!

Answer 18

@Nnesha

Answer 19

your welcome

Answer 20

You want to find the IQ score \(k\) such that
\[P(X>k)=0.2\]
where \(X\) is the random variable denoting IQ scores. With mean 110 and standard deviation 25, you have
\[P\left(\frac{X-110}{25}>\frac{k-110}{25}\right)=P\left(Z>\frac{k-110}{25}\right)=0.2\]
The probability 20% has an associated Z score of \(z\approx0.845\). So the score \(k\) satisfies the equation,
\[\frac{k-110}{25}=0.845\]

Answer 21

What exactly is a percentile though..? @sithsandgiggles

Answer 22

If a score \(k\) lies in the 80th percentile, that means 80% of the scores are below \(k\). In other words, \(k\) is the cutoff for the bottom 80% and the top 20% of scores.