| Class Interval | Frequency\[({{f}_{i}})\] | Class mark \[({{x}_{i}})\] | \[{{d}_{i}}={{x}_{i}}-a\] | \[{{f}_{i}}{{d}_{i}}\] |
| 0 -50 | \[{{f}_{1}}\] | - 600 | ||
| 50 - 100 | \[{{f}_{2}}\] | |||
| 100 - 150 | 3 | 0 | ||
| 150 - 200 | 2\[{{f}_{1}}\] | |||
| 200 - 250 | 2\[{{f}_{1}}\] | |||
| Total | 24 |
A) 125.5
B) 131.25
C) 137
D) 150
Correct Answer: B
Solution :
(b): One has to fill the table first a = 125 = Class mark of interval (100 ? 150) \[{{f}_{1}}=6,{{f}_{2}}=1,2{{f}_{1}}=12;2{{f}_{2}}=2\] Now mean \[=a+\frac{\sum{{{f}_{i}}{{d}_{i}}}}{\sum{{{f}_{i}}}}=125+\frac{150}{24}=131.25\]
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