Interpolation

Question 1

Q1

Answer 1

LB

Question 2

Q2

Answer 2

Median

Question 3

Q3

Answer 3

UB

Question 4

IQR

Answer 4

Q3-Q1

Question 5

How do you find Q2?

Answer 5

Frequency/2 to find position of item
See what group it is in
On a line top row = position of first cumulative frequency value at beginning, last number at end of line and q2 somewhere in between
On line bottom row = LB and UB and Q2 in line with item
n-small number/big number-small number = Q2-LB/UB-LB
Cross multiply to find Q2

Question 6

How do you find Q1 or Q3?

Answer 6

Same basic principle as median
Except at start for Q1 do frequency/4 and for Q3 do 3/4 X frequency

Question 7

How do you find a percentile, for example 10th?

Answer 7

Frequency/10 (percentage) = item
Same as b4
P10 = answer

Question 8

What do you do if you are looking for the position of the median in a table and n/2 is a decimal (n.5)?

Answer 8

If decimal, round up
If whole number, use halfway between two integers, e.g. 2nd and 3rd