Measures of Central Tendency

Question 1

Ungrouped Mean (x̄)

Answer 1

(Summ Xi) / N

Question 2

Ungrouped Median (x͂)

Answer 2

Middle value

First, array;
Odd number of observation - one middle value
Even number - average of the two middle values

Question 3

Ungrouped Mode (Mo or M^)

Answer 3

Most frequent in the observations

Nothing is more frequent = no mode

Question 4

Grouped Mean

Answer 4

(Summ fx) / N:

f: corresponding frequency of the class limit
x: midpoint
N: total frequency

Question 5

Grouped Median

Answer 5

LBmedc + ((N/2 - cf<) / Fmedc) i;

i = class width

Use N/2 to find median class, find where it lies between the cf< values and choose the higher cf.

Question 6

Grouped Mode

Answer 6

LBmodc + ((FA / (FA + FB)) i)

Modal class = class with highest frequency

FA: frequency above the modal class
FB: frequency below the modal class