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Your guide to a winning display. (TABLES, CHARTS, AND GRAPHS.

How do you keep track of the data from your science experiment? And how do you turn the collected information into something visually interesting, such as charts and graphs? First, read "Hit the Waves" on p. 18. Then, follow this step-by-step guide to practice making tables, graphs, and charts.

1. Data Table

Use a data table to record your experiment findings. An organized data table should list your independent variables clearly. It should also have blank spaces for you to fill in the data from your experiment. Suppose you want to find out how Atlantic hurricane strength has varied from year to year. Hurricanes are categorized on a strength level scale of 1 through 5. The stronger the storm is, the higher is its category number. The category numbers are your independent variables. And the number of hurricanes is your dependent variable.

To make a data table:

1. Draw a blank data table.

2. Give your table a title that identifies your variables ("The Yearly Change in Hurricane Strength").

3. Label the column on the left as the independent variable (Category). Underneath, list the category numbers (1, 2, 3, 4, and 5).

4. Label the columns to the right as the dependent variable (Number of Hurricanes). Draw boxes under these columns in which you can record the results in each year for each category.

5. Include columns at the far right to record the average number of hurricanes for each category. To calculate the average, simply find the total number of hurricanes in each category. Then divide the total by the number of years.

Your Turn: Complete the data table by calculating the average number of hurricanes for categories 2, 3, 4, and 5. Round your answers to the nearest tenth.

2. Bar Graph

Use a bar graph to compare your variables.

A bar graph is a great way to show how the independent variables stack up against each other. The graph below compares the number of hurricanes for each category in 2004.

To make a bar graph:

1. On graph paper, draw a set of axes (x and y).

2. Give your bar graph a title ("Hurricane Strengths in 2004").

3. Label the horizontal (x) axis with your independent variable (Category), including a label of each category number (1, 2, 3, 4, and 5).

4. Label the vertical (y) axis with your dependent variable (Number of Hurricanes) and a scale from 0 to at least the highest number in your dependent variable results.

5. For each independent variable, draw a solid bar to the height of the corresponding value of the dependent variable. Example: The number of category 1 hurricanes is 2. Draw a bar above the "1" label on the x-axis to the "2" mark on the y-axis.

Your Turn: Use the information in the data table on the previous page to complete the bar graph.


3. Line Graph

Use a line graph to pinpoint changes in your data. Choose a line graph when you want to see how continuous changes to the independent variable affect the dependent variable. For example, instead of comparing hurricane categories, you choose to focus on how the number of hurricanes in category 4 changed from year to year. The independent variable is now the year, and the dependent variable is the number of hurricanes.

To make a line graph:

1. On graph paper, draw a set of axes (x and y).

2. Give your line graph a title (The Number of Category 4 Hurricanes From 2002 to 2004).

3. Label the x-axis with your independent variable (Year) with the values of the independent variable (2002, 2003, and 2004).

4. Label the y-axis with your dependent variable (Number of Hurricanes). Use a scale from 0 to at least the highest number in your dependent variable results.

5. Plot a point on the graph for each piece of data. Example: The number of category 4 hurricanes in 2002 was 1. To locate this point on your graph, draw an imaginary vertical line from the "2002" mark on the x-axis. Then, draw an imaginary horizontal line from the "1" mark on the y-axis. Plot the point where the imaginary lines intersect.

6. Once you've plotted the points for all your data, connect the points.


4. Pie Chart

Use a pie chart to illustrate numbers expressed in percentages of a whole,

A pie chart is a circle divided into wedge-shaped sections. The circle represents 100 percent. Wedges inside that circle represent data that are percentages of the whole.

Suppose you decide to graph the percentage of hurricanes in each category that occurred during 2004. The total number of hurricanes in 2004 represents 100 percent. And each hurricane category represents a different wedge of the pie chart.

To make a pie chart:

1. Use a compass to draw a circle.

2. Give your pie chart a title ("Profile of Hurricane Strengths in 2004").

3. Mark the center of the circle with a point; this is where each pie "slice," or wedge, will start.

4. Measure a wedge for each independent variable (Category 1, 2, 3, 4, or 5). First, convert your data into percentages. Do so by dividing the number of hurricanes in each category in 2004 by the total number of hurricanes in that same year.

Example: Two of nine hurricanes in 2004 were Category 1 hurricanes. 2 / 9 = .22 or 22% when rounded to the nearest tenth. Then convert your data from percentages to angle degrees. Example: 22 percent of the total number of hurricanes in 2004 were a category 1, so the pie wedge for category 1 would be 22 percent of the 360[degrees] circle, or 79[degrees] (360 x .22 = 79.2, rounded to 79). Position a protractor at the center point of the circle. Mark 0[degrees] and 79[degrees] angles with points on the edge of the circle. Draw a line from these points to the center of the circle.

5. Label the wedge (include its percentage).

6. Measure your next wedge from the edge of the first. When finished, the entire circle should be filled and the angles of the wedges should add up to 360[degrees].*

Your Turn: Calculate the percentages of hurricanes in 2004 for the other categories in the data table. Use this information to complete the pie chart.



Category 2: 1; Category 3: 1.3; Category 4: 1.7; Category 5:07





Profile of Hurricane Strengths in 2004

Category 1 22%
Category 2 11%
Category 3 22%
Category 4 33%
Category 5 11%

Note: Table made from pie chart.
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Publication:Science World
Geographic Code:1USA
Date:Sep 18, 2006
Previous Article:Science News.
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