The following table gives the distribution of a lifetime of 400 neon lamps.

Lifetime (in hours)	Number of lamps
1500-2000	14
2000-2500	56
2500-3000	60
3000-3500	86
3500-4000	74
4000-4500	62
4500-5000	48

Find the median lifetime of a lamp.

Data:

n = 400 &$\frac{n}{2}$ = 200

Median class = 3000 – 3500

Therefore, l = 3000, C_f = 130,

f = 86 & h = 500

Median = 3000 + ($\frac{200-130}{86}$) × 500

= 3000 + ($\frac{35000}{86}$)

= 3000 + 406.97

= 3406.97

Therefore, the median lifetime of the lamps = 3406.97 hours