GraphingGraphing

Makes our life simpler!

Why do we use graphs?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?What are the parts of a graph?

Independent variable:Independent variable:– Goes on Goes on “x”“x” ( (horizontalhorizontal) axis) axis– Controlled by the experimenterControlled by the experimenter

Dependent variable:Dependent variable:– Goes on Goes on “y”“y” ( (verticalvertical) axis) axis– Result of applying the independent variableResult of applying the independent variable

Let’s do a practice problem!Let’s do a practice problem!

Determining variablesDetermining variablesThe 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 = yearANS: IND = year

DEP = pH levelDEP = pH level

Setting up your graphSetting up your graphNow we know the variables, so we know where to plot them

– On X axis (independent)• Year

– On Y axis (dependent)• pH pHp

HYearYear

Plotting your dataPlotting your data

You are now able to plot your data

YearYear

pHpH

Interpreting your graphInterpreting your graph

What is the What is the trendtrend in pH of this lake over 16 in pH of this lake over 16 years?years?

– pH decreasespH decreases

– pH becomes more acidicpH becomes more acidic

What environmental condition(s) could’ve What environmental condition(s) could’ve caused this trend?caused this trend?

– Burning fossil fuelsBurning fossil fuels

– More factories in the areaMore factories in the area

– More industrializedMore industrialized

– More carsMore cars

What’s wrong with these graphs?

Types of relationships determined Types of relationships determined by graphsby graphs

Direct relationship– BOTH variables INCREASE– Can you sketch a graph that shows this?

Types of relationships determined Types of relationships determined by graphsby graphs

Indirect relationship:– Independent variable increases, dependent

decreases– Can you sketch a graph with this relationship?

Types of relationships determined Types of relationships determined by graphsby graphs

Cyclic relationship:Cyclic relationship:– Shows repeating of same event over timeShows repeating of same event over time– Can you sketch a graph that shows a cyclic Can you sketch a graph that shows a cyclic

relationship?relationship?

Time

Types of relationships determined Types of relationships determined by graphsby graphs

Stable (no change):– Dependent variable stays the same as

independent increases– Can you sketch a graph showing stability?

Comparing rates of change using Comparing rates of change using graphsgraphs

The The angleangle of plotted line tells us the rate of plotted line tells us the rate– The STEEPER the line, the FASTER the rateThe STEEPER the line, the FASTER the rate– Which of the following graphs has a faster rate?Which of the following graphs has a faster rate?