Frequency tables
- A frequency table shows how often each value or class occurs. Tallies help you count as you go.
- A grouped frequency table uses class intervals, such as 0 ≤ t < 10. Choose classes that don't overlap and cover all the data.
Two-way tables
- A two-way table shows two variables at once, such as gender and favourite sport. Rows and columns have totals.
- To complete one, use the fact that each row and column adds up to its total. Work with whichever row or column has only one missing value.
- You can find proportions from a two-way table, such as the fraction of girls who chose tennis.
Reading and summarising tables
- Tables of secondary data (such as ONS tables) can be large. Pick out the rows and columns you need and check the units, such as "thousands".
- Percentages make groups of different sizes easier to compare. Percentage = part ÷ total × 100.
- Rounding makes tables easier to read, but totals may no longer add up exactly.
Key terms
- Frequency
- The number of times a value occurs.
- Frequency table
- A table showing how often each value or class occurs.
- Tally
- Marks used to count, grouped in fives.
- Two-way table
- A table showing two variables at once.
- Class interval
- A range of values used to group data.
- Relative frequency
- A frequency as a fraction or percentage of the total.