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Question

# Question 1 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. Number of plants0−22−44−66−88−1010−1212−14Number of Houses1215623 Which method did you use for finding the mean, and why?

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Solution

## Let us find class marks (xi) for each interval by using the relation: Class Mark (x_i)=Upper class limit + lower class limit2 Now we may compute xi and fixi as following Number of plantsNumber of Houses (fi)xifixi0−2111×1=12−4232×3=64−6151×5=56−8575×7=358−10696×9=5410−122112×11=2212−143133×13=39Total20 162 From the table we may observe that: Mean (¯x)=∑fixi∑fi=16220=8.1 So, mean number of plants per house is 8.1. We have used the direct method as values of class marks (xi) and fi are small.

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