Graphingin

Science Class

Why do we use graphing? A useful tool in science Makes data easier to interpret and make

conclusions Visual characteristics of a graph make

trends in data easy to see Helps us to "predict" data that is not

measured on the graph.

• There are 3 different types of graphs:–Bar graphs–Pie graphs–Line graphs

• Each type is used in different situations

Types of Graphs

Used to show relationships between groups

The items being compared do not need to affect each other.

Fast way to show big differencesEasy to read

Bar Graphs

Used to show how a part of something relates to the whole

Used to show percentages effectively

Circle or Pie Graph

Used to show change over time.Makes it clear to see trends by the rises and falls of the line graph

Line Graphs

Graphing Steps1. Decide what type of graph to use2. Identify the variables3. Determine the range4. Determine the scale5. Number and label each axis6. Plot the points7. Draw the graph8. Give your graph a title

Choosing the Right GraphBar graph if you are not looking for trends over time and the categories are not parts of a whole

Pie chart if you need to compare different parts of a whole, time is not a factor and there are not too many categories

Line graph if you need to see how a quantity changes over time

Identify the Variables• Independent Variable• Experimenter manipulated (the thing you

changed)• x axis (horizontal)

• Dependent Variable• Depends on the independent variable (how

did the independent variable change it?)• y axis (vertical)

Determine Range and Scale Subtract lowest value from the

highest value - this is your range

Create a scale that best fits your data - spread out your graph as much as possible to make your graph more readable

Number and Label Each Axis

Number the axes keeping in mind your range

Label each axis so that anyone reading your graph can understand what the graph means

Include units of measure

Plotting

Plot each data value on the graph with a dot.

You can put the data number by the dot if it does not clutter your graph.

DrawingIn some cases, you will connect the data points with a straight line

A “Best Fit Line” is a curved or straight line that best fits the data points.

Most graphs of experimental data are drawn as Best Fit Lines

Allows us to InterpolateAllows us to Extrapolate

Interpolation

Interpolate: predicting data between two measured points on the graph.

Extrapolation

Extrapolate: extending the graph, along the same slope, above or below measured data.

Title Your title should clearly tell what

the graph is about If your graph has more than one

set of data, provide a "key" to identify the different lines