Range, Quartiles, Deviation

Question 0

What is the sentence to remember variance?

Answer 0

Mean of the squares minus the square of the means

Question 1

What is the formula for variance?

Answer 1

∑x^2 ( ∑x )^2
—— - ( —-)
n ( n )

Question 2

What is the relationship between standard deviation and variance?

Answer 2

Standard deviation =
________
|variance

Question 3

Formula for standard deviation when in a table, where f=frequency and x= mid-point of class:

Answer 3

________________
| ∑fx^2 ( ∑fx )^2
| ——- - (—— )
| ∑f ( ∑f )

You must add columns to your table for mid-point, fx and fx^2.

Question 4

Interpercentile range:

Answer 4

Pm - Pn

You will be told m and n, e.g interpercentile range of 90% to 10%

Question 5

To calculate the xth percentile:

Answer 5

x
Px = —- * n
100

Question 6

Once you have calculated the xth percentile, use interpolation to calculate. Work out how much it is in the boundary then…

Answer 6

percentile - CF of start of boundary
————————————————
end of boundary - start of boundary

Question 7

Does coding through addition or subtraction change the standard deviation of the data?

Answer 7

No.

Question 8

Does coding through multiplication or division change the standard deviation of the data?

Answer 8

Yes