Understanding Graphing Worksheet

Graphs appear not only in textbooks and scientific journals, but also in newspapers and popular magazines. They are useful'because they clearly show relationships between two or more variables. Two of the most common graphs are bar and line graphs.

Bar graphs compare several variables according to one characteristic. For example, the bar graph below compares four kinds of cereal according to the number of calories each contains in 28 grams.

Number Of Calories Compared to Brands of Cereal

130

120

Ito

100

Sugar Circles Oat Boats Honey HunkS

Brands Of Cereal (23 grams)

l . Look at the numbers used on the vertical axis. What would happen to the bars on the graph if these numbers were changed to 100, 150, 200, and 300?

2. How would the graph change if the numbers on the vertical axis staffed with O and increased in increments of 10?

3. How does the enrollment in physical science comparewith that in chemistry over the years? Do you see any

trends?

4. Why does this graph include a legend?

Notice that the independent variables in both graphs (the kind of Brands of Cereal and the Years) are plotted along the horizontal axis. Independent variables are chosen or changed by the experimenter. The dependent variables (the Number of Calories and the Number of Students) are plotted along the vertical axis. Dependent variables change whn th independent variable changes. Notice, too, that both graphs include titles and labels for the variables.

To practice making a bar graph, let's compare the number ofstudents in several high schools. School A has 850, school B has 600, schdol C has 1200, school D has 900, andschool E has 350.

Line graphS, such as the one below, show a change in one or more variables over time. They can also illustrate a trend.

Students Enrolled inPhysical Science and

Chemistry at North High School Vs. Years

on the horizontal axis. 10. In a line graph for these data, what would be the range of numbers for independent variable and on which axis would it be

8. Considering the range of numbers, what would be appropriate numbers to use on the vertical axis? 11. In a line graph for these data, what would be the dependent variable and on which axis would it be

the levels listed above.

Year Patients Wanting Glasses Patients Wanting Contact Lenses

1984 37 42

1985 29 61

1986 32 74

1987 25 74

1988 17 86

9. How is comparing school enrollment in a graph better 12. Considering the highest and lowest number of patients just listing the numbers in a sentence? for each year, what numbers would be the most appropriate to list on the vertical axis?

On the back side of the graph paper, draw the line graph. Be sure to label the, variables and include a title. use a legend toindicate each category of patient. Mark the points on the graph that show the number of patients who asked for glasses and Tp practice makjn< a line graph, let's say an optometrist has number who requested contact lenses for each year.noticed an increase in the number of her patients requesting contact lenses. She wonders how this number compares With the Now connect the points that you have plotted in each category. number of. people asking for glasses during the past five years.The chart below lists her raw data.

13. What trends does the graph indicate?

life.