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Question
Below is the given frequency distribution of words in an essay
| Number of Words | Number of Candidates |
| 600 – 800 | 8 |
| 800 – 1000 | 22 |
| 1000 – 1200 | 40 |
| 1200 – 1400 | 18 |
| 1400 - 1600 | 12 |
Find the mean number of words written.
Solution
| (Number of words) | Class Mark | (Number of candidates) | fiXi |
| Class intervals | Xi | Frequency | |
| fi | |||
| 600 – 800 | 700 | 8 | 5600 |
| 800 – 1000 | 900 | 22 | 19800 |
| 1000 – 1200 | 1100 | 40 | 44000 |
| 1200 – 1400 | 1300 | 18 | 23400 |
| 1400 – 1600 | 1500 | 12 | 18000 |
| Total | ∑fi=100 | ∑fiXi=110800 |
Mean=
`barX=(Sigmaf_ix_i)/(Sigmaf_i)=110800/100=1108`
∴ Mean number of words written in an essay is 1108.
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