Here, we observe that, 5 students have scored marks below 10 i.e. it lies between class interval 0-10 and 9 students have scored marks below 20. So, (9-5)=4 students lies in the class interval 10-20. Continuing in the same manner, we get the complete frequency distribution table for given data.
Here, (assumed mean)a=45
and (class width)h=10
By step deviation method. `"Mean"(bar(x))=a+(sumf_(i)u_(i))/(sumf_(i))xxh=45+(29)/(85)xx10=45+(58)/(17)`
=45+3.41=48.41
