Notes: Graphing

Setting Up a Graph X axis- Independent Variable This is the variable you controlled or manipulated. Y axis- Dependent Variable This is the variable measured or observed during an experiment

Graphing Rules

Rule #1 Use a Pencil!

Rule #2 Always draw neat lines with a ruler or straight edge.

Rule #3 Label the X-axis and y-axis And include UNITS! (independent variable) and y-axis (dependent variable) And include UNITS! Example: If your X-axis is labeled “TIME,” you must put the unit in parentheses (hours, days, years, etc.)

Rule #4 Use an appropriate scale for each axis Graph must take up at least 75% of given space Graphs do not have to start at zero if your data does not include zero.

Rule #5 Title your graph

Rule #6 Provide a key (color or pattern) when using the same graph for multiple independent variables.

Types of Graphs

Bar Graphs Used to show comparisons of multiple objects one variable is non numerical (e.g. place, color) there are no independent or dependent variables

Pie Graph use to compare proportions in different categories one variable is a category one variable is a count shows parts of a whole

Line Graphs Use to show response to a manipulated variable or relationship between two variables. One variable (the Independent) affect the other (the dependent). Date is continuous for both variables

Best Fit Line If the points form a straight line….. draw the best straight line through them.

Best Fit Line If a point is not on the line ….. Re-test this measurement again if applicable. x This is called an outlier. You can decide to ignore outlier points.

Curved Graphs J-Curve: If the points form a curve…. Draw a freehand curve of best fit. J-Curve: Usually shows slow then rapid growth of a population

Curved Graphs S-Curve: If the points form a curve…. Draw a freehand curve of best fit. S-Curve: Shows slow then rapid growth until the population stabilizes