Question

The mean of the following distribution is 57.6 and the sum of its frequencies is 50, find the missing frequencies f1 and f2.
Class : 0–20 20–40 40–60 60–80 80–100 100–120
Frequency: 7 f1 12 f2 8 5 .

Answer 1

Mean:
The mean of a number of observation is the sum of the values of all the observations divided by the total number of observations.

Mean=sum of all the observations/total number of observations
Direct method:
In this method find the class marks of class interval. These class marks would serve as the representative of whole class and are represented by xi. For each class interval we have the frequency( fi) corresponding to the class mark (xi).

CLASS MARKS =( lower limit + upper limit)/2
Then find the product of fi, & xi for each class interval. Find Σfi & Σfixi.

Use the formula :
Mean = Σfixi/ Σfi

SOLUTION IS IN THE ATTACHMENT.

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Answer 2

Answer:

The value of f1 = 8

and the value of f2 = 10

Step-by-step explanation:

For detailed method see the attachment

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