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

Light time (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 life.

We can find cumulative frequencies with their respective class intervals as below:

Median class = 3000-3500

l = 3000, f = 86, F = 130, h = 500

Median = l + * h

= 3000 +

= 3406.98 hours

So, median life time is 3406.98 hours.