Graphing Makes our life simpler!

Why do we use graphs? It’s an organized way to express data Allows for easy interpretation of the data

What are the parts of a graph? Independent variable: –Goes on “x” (horizontal) axis –Controlled by the experimenter Dependent variable: –Goes on “y” (vertical) axis –Result of applying the independent variable Let’s do a practice problem!

Determining variables The table shows data collected on the pH of a lake in the Adirondacks over 16 years. Based on the table, what is the independent variable and what is the dependent variable? –ANS: IND = year DEP = pH level DEP = pH level

Setting up your graph Now we know the variables, so we know where to plot them –On X axis (independent) Year –On Y axis (dependent) pH pH Year

Plotting your data You are now able to plot your data Year pH

Interpreting your graph What is the trend in pH of this lake over 16 years? –pH decreases –pH becomes more acidic What environmental condition(s) could’ve caused this trend? –Burning fossil fuels –More factories in the area –More industrialized –More cars

What’s wrong with these graphs?

Types of relationships determined by graphs Direct relationship –BOTH variables INCREASE –Can you sketch a graph that shows this?

Types of relationships determined by graphs Indirect relationship: –Independent variable increases, dependent decreases –Can you sketch a graph with this relationship?

Types of relationships determined by graphs Cyclic relationship: –S–S–S–Shows repeating of same event over time –C–C–C–Can you sketch a graph that shows a cyclic relationship? Time

Types of relationships determined by graphs Stable (no change): –Dependent variable stays the same as independent increases –Can you sketch a graph showing stability?

Comparing rates of change using graphs The angle of plotted line tells us the rate –The STEEPER the line, the FASTER the rate –Which of the following graphs has a faster rate?