To find out the concentration of SO2 in the air (in parts per million,

To find out the concentration of SO2 in the air (in parts per million, i.e., ppm), the data was collected for 30 localities in a certain city and is presented below: Concentraion of So2 (in ppm) Frequency0.00 - 0.04 40.04 - 0.08 90.08 - 0.12 90.12 - 0.16 20.16 - 0.20 40. 20 - 0.24 2Find the mean concentration of SO2 in the air.

Answer»

We may calculate class marks (x_i) for each interval by using the relation

x_i \(=\frac{Upper\,class\,limit+lower\,class\,limit}{2}\)

Class size = 0.04

Now taking 0.14 as assumed mean (A), we can calculate as follows:

Mean (x̅) = A + \(\frac{\sum f_iu_i}{N}\times h\)

\(=0.14+\frac{-31}{30}\times(0.04)\)

\(=0.14-0.04133\)

\(=0.099\)ppm

SO,

mean concentration of SO₂ in the air is 0.099 ppm