25.2 Cumulative frequency — Practise

1. H Frequencies are $4, 7, 5, 3$. Write the cumulative frequencies.
2. H Classes $0<x\leq10$, $10<x\leq20$, $20<x\leq30$ have frequencies $5,8,7$. Give the cumulative frequencies and graph coordinates, including $(0,0)$.
3. H A cumulative frequency graph represents 40 observations. At which cumulative frequency do you estimate the median?
4. H A cumulative frequency graph represents 60 observations. State the cumulative frequencies for estimating the lower and upper quartiles.
5. H Cumulative frequency is $12$ at time 10 minutes and $25$ at 20 minutes. How many observations lie in the class above 10 and up to 20 minutes?
6. H Classes are $0<t\leq5$, $5<t\leq10$, $10<t\leq15$ with frequencies $2,9,4$. Give the cumulative frequency coordinates after $(0,0)$.
7. H A survey contains 80 values. Which cumulative frequency locates the median?
8. H On a cumulative frequency graph for 100 values, estimates read $Q_1=12$ and $Q_3=28$. Work out the IQR.
9. H A grouped table has frequencies $6, 3, 8$. Find the final cumulative frequency and state whether a cumulative frequency graph can decrease.