Question

The number of students absent in a class was recorded every day for 120 days and the information is given in the following
No of students absent (x): 0 1 2 3 4 5 6 7
No of days (f): 1 4 10 50 34 15 4 2

Find the mean number of students absent per day.

Answer 1

ASSUMED MEAN METHOD :  

In this method, first of all, one among xi 's is chosen as the assumed mean denoted  by ‘A’. After that the difference ‘di’ between ‘A’ and each of the xi's i.e di = xi - A is calculated .  

ARITHMETIC MEAN =  A +  Σfidi / Σfi

[‘Σ’ Sigma means ‘summation’ ]

★★ We may take Assumed mean 'A’ to be that xi which lies in the middle of x1 ,x2 …..xn.

FREQUENCY DISTRIBUTION TABLE IS IN THE ATTACHMENT  

From the table : Σfidi = - 57 ,Σfi = 120,  

Let the assumed mean, A = 4

ARITHMETIC MEAN =  A +  Σfidi / Σfi

ARITHMETIC MEAN =  4 + (- 57/120)

= 4 - 57/120

= 4 - 0.475

= 3.525

ARITHMETIC MEAN = 3.525 ≈ 3.53 (approximate)  

Hence, the mean number of students absent per day is ≈ 3.53 (approximate).  

HOPE THIS ANSWER WILL HELP YOU….

Answer 2

Mean=(Σfixi)/(Σfi​)

= 423/120

= 3.525

Therefore ,

Mean Number of students absent

per day = 3.525

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