Business Statistics

Chapter 3 | Measures of Central Tendency 99

TABLE 3.28

Class, frequencies, and cumulative frequencies for Example 3.19

Class Frequency Cumulative frequency

0–5 4 4

5–10 5 9

10–15 6 15

15–20 10 25

20–25 11 36

25–30 9 45

30–35 4 49

35–40 1 50

Here,

50

12.5

4 4

= =

N

Hence, lower quartile class is 10–15 (Table 3.28).

1

( /4)-

= + ´

N c

Q i

f

12.5 9

10 5

6

-

= + ´

= 10 + 2.91

= 12.91

50

3 3 37.5

4 4

N

é

ê

= ´ =

ê

ë

Hence, upper quartile class is 25 – 30 (Table 3.28)

3

3 ( /4)-

= + ´

N c

Q i

f

37.5 36

25 5

9

-

= + ´

= 25 + 0.83

= 25.83

So, rst quartile Q

1

= 12.91 and third quartile Q

3

= 25.83.

3.7.2 Using MS Excel for Quartiles Computation

For computing quartiles using ...