Data tables and

Graphs

Nature of Science

Data Tables

Organize data. Neat rows and columns. A place to record data. Communicate to others.

Show relationships. Each data item represents the

relationship between the row value and column value.

The Population

Data TablesFor Example:

Population of the United States

Year Population(in millions)

1900 76

1910 92

1920 105.7

1930 122.8

1940 131.7

1950 151.3

1960 179.2

1970 203.2

1980 226.5

1990 251.4

Each data item is connected to a row label and a column label.

Here the number 92 shows

in 1910

Graphs

We will use three types of graphs Circle Graphs (Pie Charts)

Bar Graphs

Line Graphs

Use a circle graph whenever the data is in percent. The entire circle represents

100%.

Each section should be labeled: Name Number

A circle graph should also have a title.

Circle (Pie Chart) Graphs

Each section is sized according to the size of its data.

You may also use letters or colors that refer to names in a key.

We use a Bar graph whenever the data represents separate categories of data. The categories are listed along

the horizontal axis.

A measurement scale is constructed along the vertical axis.

Bar Graphs

A bar graph should have: a title a label for each axis a key if multiple sets of data are displayed.

# o

f Stu

dents

When you have one category of data that is changing. A measurement scale is

constructed along the vertical axis and horizontal axis.

Each scale should have equal spacing. (But NOT necessarily the same.)

Line Graphs

The graph should have: A title Labels on each axis A key if multiple sets of data are graphed.

Important! The data values NEVER go on the horizontal or vertical axis.

The smallest value on the axis should be a little less than, or equal to, the smallest data value.

Line Graphs

Create equal increments to mark the axis.

The largest value should be greater than, or equal to, the largest data value.

Independent and Dependent variables.

When plotting data, The independent variable

is measured along the horizontal axis.

The dependent variable is measured along the vertical axis.

Line Graphs

Data points represent the intersection of a horizontal value and a vertical value.

Line Graphs

Do NOT connect the dots!

Best Fit lines represent the general trend of the data.

Use a ruler.

Line Graphs

Not from the smallest data point to the largest data point.

Try to draw a line that keeps all of the points as close to the line as possible.

Mark the trend of the data.

Interpolation and Extrapolation

Use the “best fit line” to make inferences about data points not measured.

Line Graphs

Interpolation: Making inferences about data values between the data points.

We could interpolate that in the third year, the growth would be about 7m.

Interpolation and Extrapolation

Line Graphs

Extrapolation: Making inferences about data values outside the range of the measured data.

12

30

25

Use the “best fit line” to make inferences about data points not measured.

We could extrapolate that in the 12th year, the growth would be about 28m.

Slope has meaning!

How do you calculate slope?

Line Graphs

∆Y/∆X Remember: ∆ means (final – Initial)

On some graphs it is meaningless. But we must always check.

Slope has meaning!

How do you calculate slope?

Line Graphs

∆Y/∆X Remember: ∆ means (final – Initial)

Mass (g)

Volume (mL)

On some graphs it is meaningless. But we must always check.

It is always important to use data tables and graphs to organize

your data; so that you, and others, may make accurate and

useful inferences from your data.

Nature of Science