Page 38 - DECO504_STATISTICAL_METHODS_IN_ECONOMICS_ENGLISH

Statistical Methods in Economics

Notes Frequency Distribution

Wages Tally bars Frequency

200-300 |||| |||| ||| 13
300-400 |||| |||| | 11

400-500 |||| |||| |||| ||| 18
500-600 |||| |||| 10

600-700 |||| | 6

700-800 |||| 5

800-900 |||| |||| |||| 14

900-1000 |||| |||| || 12

1000-1100 |||| |||| | 11

Total 100

2. If the class mid-points in a frequency distribution of age of a group of persons are 25, 32, 39, 46,
53 and 60, find: (i) the size of the class interval, (ii) the class boundaries and (iii) the class limits,
assuming that the age quoted is the age completed on last birthday.
Solution: (i) The size of class interval
= Difference between the mid-values of any two consecutive classes
= 32 – 25 = 39 – 39.......60 – 53 = 7.
(ii) Since the magnitude of the class is 7 and the mid-values of the classes are 25, 32.....60, the
corresponding class boundaries for different classes are obtained by adding and subtracting
7
half the magnitude of the class interval i.e., = 3·5 to/from the mid-values to obtain
2
higher and lower class boundaries.
1st Class → 25 – 3·5, 25 + 3·5
2nd Class → 32 – 3·5, 32 + 3·5
3rd Class → 39 – 3·5, 39 + 3·5
4th Class → 46 – 3·5, 46 + 3·5
5th Class → 53 – 3·5, 53 + 3·5
6th Class → 60 – 3·5, 60 + 3·5.
Class Intervals
21·5 — 28·5
28·5 — 35·5
35·5 — 42·5
42·5 — 49·5
49·5 — 56·5
56·5 — 63·5

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