# GCSE statistics coursework help!!! How do u find outliers?

Is this right...???

IQR=UQ-LQ

IQR x 1.5=?

UQ+ ? = ??? (anything above ??? is an outlier)

LQ - ?=??? ( anything lower than ??? is an outlier)

I have tried this and have not found any outliers so i just want 2 c if this is right

thanks in advance.

### 3 Answers

- Anonymous1 decade agoFavourite answer
I remember doing this. :)

I can't remember how you do it though but i still got an A.

umm...

found this on wikianswers

Find the inter quartile range, which is IQR = Q3 - Q1, where Q3 is the third quartile and Q1 is the first quartile. Then find these two numbers:

a) Q1 - 1.5*IQR

b) Q3 + 1.5*IQR

Any observation that is below a) or above b) can be considered an outlier.

edit: Chadwick, quartiles are considered robust, meaning that they are not highly effected by outliers. This is because it takes location into account, not the values. Let's look at your data set (sorted).

2 3 6 9 13 18 21 106

position of Q1 = (8+1)/4 = 2.25

Q1 = 0.75(3)+0.25(6) = 3.75

position of Q2 = (8+1)/2 = 4.5

Q2 = (9+13)/2 = 11

position of Q3 = 3(8+1)/4 = 6.75

Q3 = 0.25(18)+0.75(21) = 20.25

Notice that none of these actually use the value 106. Let's continue.

So IQR = Q3-Q1 = 20.25-3.75 = 16.5

Q1-1.5*IQR = 3.75-1.5*16.5 = -21

Q3+1.5*IQR = 20.25+1.5*16.5 = 45

No numbers are below -21, but 106 is above 45, so it can be considered an outlier

- Anonymous5 years ago
Ask Dan Rather. If he won't tell you, call him "Kenneth" and beat him up.