The table shows the lifetimes of a sample of electric light globes.
Life ( l hours)
Number of globes
0≤l<500
5
500≤l<1000
17
1000≤l<2000
46
2000≤l<3000
79
3000≤l<4000
27
4000≤l<5000
4
a. Draw a cumulative frequency graph for the data.
b. Estimate the median life of a globe.
c. Estimate the percentage of globes which had a life of 2700 hours or less.
d. Estimate the number of globes which had a life between 1500 and 2500 hours.