Page 491 - Canadian BC Science 9

6. If it is possible, draw a line that connects all of the points on your graph. This might not be possible. Scientific investigations often involve quantities that do not change smoothly. On a graph, this means that you should draw a smooth curve (or straight line) that most closely fits the general shape outlined by the points. This is called a line of best fit. A best-fit line often passes through many of the points, but sometimes it goes between points. Think of the dots on your graph as clues about where the perfect smooth curve (or straight line) should go. A line of best fit shows the trend of the data. It can be extended beyond the first and last points to indicate what might happen.
7. Give your graph a title. Based on these data, what is the relationship between the number of students using recycling bins and the number of recycling bins?
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Constructing a Bar Graph
Bar graphs help you to compare a numerical quantity with some other category at a glance. The second category may or may not be a numerical quantity. It could be places, items, organisms, or groups, for example.
Example
To learn how to make a bar graph to display the data in Table 3 on the next page, examine the graph in the column next to the table as you read the steps that follow. The data show the number of days of fog recorded during one year at one weather station in each of the provinces and territories.
Instant Practice—Line Graphs
The level of ozone in the upper atmosphere is measured in Dobson units (all the ozone present in a column of air above a particular point). Using the information in the table below, create a line graph showing what happened to the amount of ozone over Antarctica during a period of 40 years.
Table 2 Ozone Levels in Upper Atmosphere
Year
Total Ozone (DU)
1960
300
1965
280
1970
280
1975
275
1980
225
1985
200
1990
160
1995
110
2000
105
1234
Number of Recycling Bins
Number of Students Using Recycling Bins
Science Skill 5 • MHR 473