A survey was conducted by a group of students as a part of their environment awareness programme, in which they collected the following data regarding the number of plants in 20 houses in a locality. Find the mean number of plants per house.

Question :

Number of plants0 – 22 – 44 – 66 – 88 – 1010 – 1212 – 14
No. of houses1215623

Which method do you use for finding the mean and why ?

Solution :

Number of PlantsNumber of houses \(f_i\)Mid-value xfx
0 – 2111
2 – 4236
4 – 6155
6 – 85735
8 – 106954
10 – 1221122
12 – 1431339
\(\sum f_i\) = 20\(\sum f_ix_i\) = 162

Mean = \(\sum f_ix_i\over \sum f_i\) = \(162\over 20\) = 8.1

Here, we have used direct method because numerical values of \(x_i\) and \(f_i\) are small.

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