Frequency and charts
Frequency and charts
A bar chart draws a frequency table: a bar for each answer, and the bar’s height is the answer’s frequency.
This is the favourite sport of the 30 pupils of class 8A:
| Sport | football | basketball | swimming | tennis | dance |
|---|---|---|---|---|---|
| Frequency | 11 | 8 | 5 | 2 | 4 |
- The horizontal axis: the answers – here, the sports.
- The vertical axis: the frequency – the number of pupils, in equal steps: 0, 2, 4, …
- All the bars are the same width, with gaps between them.
From 8A’s chart you read what the table says, only faster:
- The most frequent: the tallest bar – football, 11 pupils.
- The least frequent: the shortest bar – tennis, 2 pupils.
- How many answered in all: add the heights of all the bars, .
- How many more: subtract one height from another. Football against basketball: – 3 more pupils chose football.
A line chart shows a quantity that changes over time: a point for each time, and a line joining the points in order.
These are the minutes Noa spent on her phone each day of one week:
- The highest point: Saturday, 140 minutes. The lowest: Thursday, 60 minutes.
- Where the line goes up, the time on the phone grows; where it goes down, it shrinks.
- The biggest rise is the steepest piece, from Thursday to Friday: minutes.
- A line chart fits when the answers are times in a fixed order: days, months, years. Sports have no such order, so they get a bar chart.
A bar chart is drawn from a frequency table in four steps:
- Draw two axes: the horizontal one for the answers, the vertical one for the frequencies.
- Choose a step for the vertical axis, so that even the largest frequency fits. In 8A the largest frequency is 11, so a step of 2, up to 12.
- Draw a bar for each answer, up to the height of its frequency. All the bars are the same width.
- Write the answer under each bar, and a title on each axis.
The chart shows how the pupils of class 8C get to school.
Which way is the most frequent, and which is the least frequent?
How many pupils are there in the class?
/ – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power
/ – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power
How many more pupils walk to school than come by car?
/ – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power
/ – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power
How many pupils do not walk to school?
/ – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power
/ – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power
The chart shows how many books were borrowed from the school library in each month of the school year.
In which month were the most books borrowed? How many?
/ – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power
/ – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power
Between which two months in a row was the biggest drop?
How many books were borrowed in all from September to December?
/ – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power
/ – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power
28 pupils chose their favourite ice-cream flavour.
| Flavour | chocolate | vanilla | strawberry | lemon | pistachio |
|---|---|---|---|---|---|
| Frequency | 10 | 6 | 4 | 3 | 5 |
Draw a bar chart from the table. Choose a fitting step for the vertical axis.
The chart compares the favourite sports of the pupils of 8A and of 8B.
In which sport is the difference between the two classes the largest?
How many pupils are there in 8B?
/ – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power
/ – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power
Which chart fits each set of data – a bar chart or a line chart? Explain.
- The height of a sunflower, measured once a week for two months.
- The favourite colour of the pupils in the grade.
- The temperature at noon on each day of March.
- The number of pupils in each of the 8th-grade classes.
/ – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – check and a new line · * – times · ^ – power, ↓ – end of the power
/ – fraction bar · Tab or the arrows – between numerator and denominator, then a note above or below · Enter – a new line · * – times · ^ – power, ↓ – end of the power