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## PowerPoint Slideshow about ' Graphs An Introduction' - nikkos

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### GraphsAn Introduction

What is a graph?

A graph is a visual representation of a relationship between, but not restricted to, two variables.

A graph generally takes the form of a one- or two-dimensional figure. Although, there are three-dimensional graphs available, they are usually considered too complex to understand easily.

A graph commonly consists of two axes called the x-axis (horizontal) and y-axis (vertical).

A graph can show Discrete or Continuous data types. Data types determines which graph to use.

Discrete or Continuous

Discrete:

Data that can be separated by some interval, for example:

Recording the shoe sizes of a class – Bar graph

Continuous:

When data collected is continuous, for example:

Recording temperature – Line graph

25

Y – axis

Scale or Increments

20

All graphs (except Pie Chart) have common elements:

- Axis x and y (also z in 3D graphs)
- Axis labels
- A title
- Scales or Increments
- Can represent negative values

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Y – axis label

10

5

Origin – does not always have to start at 0,0

X-axis

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30

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50

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X-axis label

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Scale or Increments

-10

If we draw a vertical line from any point on the x-axis

Co-ordinates

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Y – axis

and a horizontal line from the y-axis

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A (3,15)

the point at which they meet gives us the co-ordinate

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B (-4,10)

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5

1

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-1

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X-axis

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C (-5,-15)

Back

See creating a line graph presentation

Line GraphsA good method of showing the relationship between two variables

Back

Bar Chart / Graph

Used to compare values in a category or between categories.

The graph shown here makes a visual comparison of the fat content of types of cheese

Bar Chart / Graph

Can be useful to study trends over time

See creating a bar graph presentation

Bar Chart / GraphMultiple (or group) bar graphs compare relationships of closely related sets

Back

See creating a pie chart presentation

Pie ChartsA pie chart is used to show how a part of something relates to the whole. This kind of graph is particularly suited to showing percentages

Back

Height (cm)

Scatter GraphDrawing a scatter graph is similar to drawing a line graph in that co-ordinates are used to plot the points. There are usually more points to be plotted in a scatter graph and the points can be in groups, therefore it is not possible to draw a line through all of the points.

A scatter graph shows how much correlation there is between two variables that you suspect may be linked for instance height and weight as shown here:

It is sometimes useful to draw a “line of best fit” to show the trend

Line of best fit

Back

Summary

A good graph:

Accurately shows the data

Grabs the reader's attention

Has a title and labels

Is simple and uncluttered

Clearly shows any trends or differences in the data

Is visually accurate (i.e., if one data value is 25 and another 50, then 50 should appear to be twice the size of 25).

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