Charts and graphs
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수업 노트
Types of Data
- Qualitative data describes qualities or categories, such as favourite colour or type of pet.
- Discrete data can only take specific values, usually whole numbers, such as the number of siblings a student has.
- Continuous data can take any value within a range, such as height or time, and is measured rather than counted.
- Choosing the right chart depends on the type of data you have.
Tally Charts and Frequency Tables
- A tally chart uses tally marks to record each occurrence of a value as data is collected.
- Tally marks are grouped in fives for easy counting.
- A frequency table shows each value or category and the number of times it occurs (its frequency).
- Frequency tables make it easy to see the most and least common values.
Bar Charts and Pictograms
- A bar chart uses rectangular bars with lengths proportional to the values they represent.
- Bars can be drawn vertically or horizontally.
- In a dual or composite bar chart, bars are grouped or stacked to compare two or more sets of data.
- A pictogram uses pictures or symbols to represent data, with a key showing what each symbol stands for.
- In a pictogram, part of a symbol can represent a fraction of the value.
Pie Charts
- A pie chart shows data as slices of a circle, where each slice represents a proportion of the whole.
- To find the angle for each slice, use the formula: angle = (frequency ÷ total frequency) × 360°.
- All the angles in a pie chart add up to 360°.
- Pie charts are best for showing percentages or proportions of different groups.
Line Graphs and Time Series
- A line graph plots ordered observations as points connected by straight lines.
- Line graphs are ideal for showing how data changes over time (a time series).
- The x-axis usually shows time and the y-axis shows the variable being measured.
- A line graph makes trends, such as increases or decreases, easy to spot.
Stem-and-Leaf Diagrams and Frequency Diagrams
- A stem-and-leaf diagram splits each data value into a stem (usually the leading digit) and a leaf (usually the last digit).
- Stem-and-leaf diagrams keep the original data values while showing the shape of the distribution.
- A frequency diagram (or histogram) uses adjacent rectangles to show the frequency of data in intervals (bins).
- In a histogram, the area of each bar is proportional to the frequency.
Choosing an Appropriate Chart
- Use a pie chart to show proportions or percentages of a whole.
- Use a bar chart to compare frequencies of different categories.
- Use a line graph to show changes over time.
- Use a scatter plot to show the relationship between two variables.
- Use a stem-and-leaf diagram to display the shape of a small data set while keeping the original values.
Spotting Misleading Graphs
- A misleading graph can distort data by using a y-axis that does not start at zero.
- Unequal intervals on an axis can make differences look larger or smaller than they really are.
- Pictures or 3D effects in pictograms and bar charts can exaggerate differences.
- Always check the scale, labels, and starting point of a graph before drawing conclusions.
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연습 문제
무료 미리 보기 — 62개 중 8개 문제. 가입하면 전부 볼 수 있어요.
1.Which type of chart is best for showing how a quantity changes over a period of time, such as annual revenue from 1990 to 2000?
Easy- APie chart
- BLine chart
- CStem-and-leaf diagram
- DPictogram
2.A pie chart is used to show percentage values. If one category is 25% of the total, what angle should its sector have?
Easy- A25°
- B45°
- C90°
- D180°
3.The label on the x-axis of a chart reads 'Distance travelled (m)'. What does the '(m)' tell you?
Medium- AThe maximum value on the axis
- BThe unit of the scale
- CThe number of data points
- DThe title of the chart
4.Which of the following are common elements of a chart? (select all that apply)
Medium- ATitle
- BAxes with scales
- CLegend or key
- DGridlines
- ECalculator
5.A histogram consists of adjacent rectangles erected over discrete intervals, with area equal to frequency.
EasyTrue or false?
6.Match each type of chart to its main use.
Medium- Pie chart
- Line chart
- Bar chart
- Scatter plot
- Show parts of a whole as percentages
- Show change over time
- Compare frequencies of categories
- Show relationship between two variables
7.Put these steps for drawing a pie chart in the correct order.
Medium- Calculate the total frequency
- Work out each category's fraction of the total
- Multiply each fraction by 360° to find the sector angle
- Draw and label the sectors
8.A bar chart showing test scores starts its vertical axis at 50 instead of 0. What effect does this have on the chart?
Hard- AIt makes differences between bars look smaller
- BIt makes differences between bars look larger
- CIt does not change the appearance of the bars
- DIt changes the actual values of the data