Bell Ringer List 5 things that all good graphs should have. (Ex: Title)

Step 1: Label Axes X-Axis Y-Axis Independent Variable: “Cause” The variable that we have chosen to change. Y-Axis Dependent Variable: “Effect” The variable that changes due to the independent variable Example: A football player kicks a ball, and it lands some distance away. Cause – independent Effect - dependent

Example (The distance “depends” on how hard the player kicks it). Example: A football player kicks a ball, and it lands some distance away. The Independent variable (X-Axis) how hard the player kicks the ball The Dependent variable (Y-Axis) the distance the ball travels (The distance “depends” on how hard the player kicks it).

Try It On Your Own Read Worksheet 1 “Making Line Graphs” Practice: Identify the Independent Variable (Cause) Identify the Dependent Variable (Effect)

Step 2: Title and Labels Labels independent variable (units) Dependent variable (units) Dependent vs. Independent Labels Write the full name include the UNITS!!! The title of the graph is always going to be written as: dependent variable vs. independent variable.

Step 3: Determine Scale Origin: Axis Scale Will always be point (0, 0) Axis Scale Must go up by consistent amount (equal intervals) Ex: Interval of 5’s (0, 5, 10, 15, …) Note: The #’s on the x-axis and y-axis do NOT need to go up by the same interval.

Step 3: Determine Scale for the axis Data range: the difference between the lowest and highest value of the data. Example: lowest: 25 degrees C highest: 110 degrees C Range: __________ degrees C 85 Number of lines on the graph: 25 85 degrees ÷ 25 lines = Adjusted scale: round-up and use 4 degrees/line 3.4 degrees/line (calculated scale)

Step 4: Plotting Points Data table Set of (x, y) coordinates Ex: the first point on the graph is located at (5, 8) Plot all of the points from the data table DO NOT connect the points on the graph

Step 5: Best-Fit Line Used to show a general trend in the data Draw a single, straight line through middle of data Must be drawn with a “straight edge” such as a ruler Note: Line may or may not go through point (0, 0) This is ok!!! Line does not need to go through any of the points Roughly same # of dots above and below line

Slope Slope measures the change between two points Rate of change

Rise/Run Method Find two “Easy” Points From point 1 to point 2 find how much to: Go up by (“Rise”) Go over by (“Run”) Slope = Rise/Run 0 1 2 3 4 5 5 4 3 2 1 0 Rise RUN Rise: 2, Run: 4. Slope 2/4 = .5

Formula Method 1. Find any 2 points on the line 0 1 2 3 4 5 5 4 3 2 1 0 Rise RUN 1. Find any 2 points on the line 2. Pick one to be point 1, the other as point 2 3. Determine coordinates (x, y) for each 4. Plug these in to the formula Point 1: (1,2) Point 2 (5, 4) 4 – 2 = 2 = .5 5 – 1 4

Example What is the slope of these graphs? Rise/Run: 7-4/3-0 = 3/3 = slope of 1 Rise/Run: 6-2/2-0 = 3/2 = slope of 1.5

Determine Slope of Lab Rat Graph Slope = Rise/Run or 32-8 = 24 4 = .8 35-5 30 5

y-intercept y-axis number where the “best-fit” line crosses the vertical (up/down) axis Gives the “initial conditions” Determine y-intercept of Lab Rat data

Bell Ringer 1. Find the slope 2. CPS students decided to collect data on the Time Spent Studying and their Test Scores. Independent variable? Dependent variable? Point 1 (0,2) Point 2 (2,6) Y2-y1 / x2-x1 = (6-2)/(2-0) = 4/2 = slope of 2 Independent: Time spent studying. Dependent: Test Scores

Answer Problem #1 Point 1 (0,2) Point 2 (2,6) y2-y1 = (6-2) = 4 = slope is 2 x2-x1 (2-0) 2

Answer Problem #2 Independent Variable (x-axis) Time spent studying Dependent Variable (y-axis) Test Score (Time Spent Studying) causes a change in (Test Score) and it is not possible that (Test Score) could cause a change in (Time Spent Studying) The test score depends upon the time spent studying