Question 31 The median of the following data is 16. Find the missing frequencies a and b, if the total of the frequencies is 70.Given
∑▒𝒇𝒊 = 70
Finding
Cummulative Freq.
Since
Median = 16
15 – 20 is median class
Median = l + (𝑛/2 −𝑐𝑓)/𝑓 × h
Where
l = lower limit of median class
h = class-interval
n = ∑▒𝑓𝑖
cf = cumulative freq.of class before median class
f = frequency of the median class
Now,
Median = l + (𝒏/𝟐 −𝒄𝒇)/𝒇 × h
16 = 15 + (70/2 − (24 + 𝑎))/15 × 5
16 − 15 = (35 − 24 − 𝑎)/3
1 = (11 − 𝑎)/3
3 = 11 − a
a = 11 − 3
a = 8
Also,
∑▒𝒇𝒊 = 55 + a + b
70 = 55 + a + b
Putting a = 8
70 = 55 + 8 + b
70 = 63 + b
70 − 63 = b
b = 7
Made by
Davneet Singh
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