Question

The quartile deviation and coefficient of quartile deviation of a continuous frequency distribution are 2 and 0.25 respectively. Find lower and upper quartiles.

Answer 1

Lower quartile = 6

Uppwr quartile = 10

Explanation:

Coefficient of quartile deviation = 0.25

Quartile deviation = 2

Coefficient of quartile deviation = (Q3 - Q1) / (Q3 + Q1)

Quartile deviation = (Q3 - Q1) / 2

Hence;

Quartile deviation = (Q3 - Q1) / 2 = 2

Q3 - Q1 = 2 * 2

Q3 - Q1 = 4 - - - - (1)

Q3 = 4 + Q1 - - - - (2)

(Q3 - Q1) / (Q3 + Q1) = 0.25

Q3 - Q1 = 4

4 = 0.25(Q3 + Q1)

Q3 + Q1 = 4 / 0.25

Q3 + Q1 = 16 - - - - (3)

Put Q3 = 4 + Q1 in (3)

4 + Q1 + Q1 = 16

4 + 2Q1 = 16

2Q1 = 16 - 4

Q1 = 12 / 2

Q1 = 6

Q3 = 4 + Q1

Q3 = 4 + 6

Q3 = 10