Question

The following table gives the distribution of the life-time of 400 neon lamps.

Find the median life-time of a lamp.

Answer 1

Total observations are n = 400

 \(\frac{n}{2}\)th observation i.e \(\frac{400}{2}\) = 200 

200 lies in the class 3000 – 3500 

∴ Median class = 3000 – 3500 

Lower boundary l = 3000 

frequency of the median class f = 86 

c.f = 130 

Class size, h = 500

= 3000 + \(\frac{70}{86}\) × 500 

= 3000 + 406.977 

= 3406.98 

∴ Median life ≃ 3406.98 hours