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Question
Given below is the frequency distribution table regarding the concentration of sulphur dioxide in the air in parts per million of a certain city for 30 days.
| Conc. of SO2 | 0.00-0.04 | 0.04-0.08 | 0.08-0.12 | 0.12-0.16 | 0.16-0.20 | 0.20-0.24 |
| No. days: | 4 | 8 | 9 | 2 | 4 | 3 |
Find the probability of concentration of sulphur dioxide in the interval 0.12-0.16 on any of these days.
Solution
The total number of trials is 30.
Remember the empirical or experimental or observed frequency approach to probability.
If n be the total number of trials of an experiment and A is an event associated to it such that A happens in m-trials. Then the empirical probability of happening of event A is denoted by P (A) and is given by
`P (A) = m/n`
Let A1 be the event that the concentration of sulphur dioxide in a day is 0.12-0.16 parts per million.
The number of times A1 happens is 2.
Therefore, we have
` P(A_1) = 2/30`
`=1/15`
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