How_to_Interpret_Graphs_new.pptx

Introduction to Graphing Background Information • Graphs are – used to visually share data and/or trends with other members of the scientific community. – transform large amounts of numbers into a much easier to understand “picture”. – help people understand the meaning of data collected in an in...

Introduction to Graphing Background Information • Graphs are – used to visually share data and/or trends with other members of the scientific community. – transform large amounts of numbers into a much easier to understand “picture”. – help people understand the meaning of data collected in an investigation or experiment. Why are graphs useful? Graphs are a quick way to visualize trends or to make comparisons. Types of Graphs • Line graphs- used to measure data over time • Bar graphs- used to compare values • Pie charts- used to compare values (usually percentages) • Scatter plots- used to show trends and relationships among a large number of data Independent or Manipulated Variable • This is the variable we can control in an experiment. Independent/manipulated variables are set up ahead of time, before you start following your procedures. • On a graph, this variable goes on the X axis. Dependent or Responding Variable • Dependent variables are measured during the experiment, after you start following your procedures. • On a graph, this variable goes on the Yaxis Graphs show us trends and relationships among data. There are generally two types of relationships that data will exhibit: inverse and direct. If one variable increases and the other decreasesthey share an inverse relationship. If both variables increase or decrease together- they share a direct relationship. Inverse Relationships- As one variable increases, the other factor decreases. Examples: As you exercise more, your risk for heart disease decreases. The farther I drive, the less distance I have to reach my destination. Direct relationships occur when the two variables increase or decrease together. Examples: The higher your temperature, the higher your perspiration rate is. As the diameter of a pipe increases, the flow of water through the pipe also increases. RULES OF GRAPHING RULE # 1 Always draw neat lines with a straight edge or ruler. RULE # 2. • Make your graph 1/2 page or 1 full page in size. RULE # 3. Wind Speed of Storms after Landfall Units on Xaxis: Always label the Xaxis with units. RULE # 4. Units on Yaxis: Always label the Yaxis with units. Wind Speed of Storms after Landfall RULE # 5 • If your graph shows more than one trial of data, or has more than 1 line, use a key. • A key can be different colored lines, lines with different textures or patterns. Wind Speed of Storms after Landfall Wind Speed of Storms after Landfall • Label THREE places on your graph RULE # 6 Title your graph at the top Wind Speed of Storms after Landfall RULE # 7 Wind Speed of Storms after Landfall Label the X-axis with the Manipulated or Independent variable. RULE # 8 • Label the Y-axis with the Responding or Dependent variable Wind Speed of Storms after Landfall RULE # 9 Number the x and y axis with a numerical sequence starting with 0, so it fills the entire axis. examples: 0, 5, 10, 15 . . . 0, 2, 4, 6, . ., 0, 0.5, 1.0, 1.5, 2.0 This is a simple line graph charting temperature. Temperature is labeled on the "y" axis and the dates (Jan 1-7) is labeled on the "x" axis. During the first week of January, which day was the coldest? January ______ 1st What was the temperature on o ~39 F January7th? ______ Which day does the temperature peak? ____ January 4th The respondent variable is the temperature, the independent variable are the dates. Practice Constructing a Line Graph Data to graph: Year 0 - 10 frogs Year 5 - 20 frogs Year 10 - 60 frogs Year 15 - 120 frogs Year 20- 120 frogs Number of Frogs 150 Time or trials are always placed on the x-axis 140 130 120 110 100 90 80 70 60 50 40 30 20 The variable goes on the Y axis. 10 0 5 10 Year 15 20 Your numbers MUST be evenly spaced for accuracy. What if time isn’t a variable on your graph? Distance (m) Usually the X axis has the independent variable (what you can manipulate or adjust) and the Y has the responding variable (what is measured/counted/observed) Multiple carts are pushed down a track with different sized weights attached to them. The distance traveled was measured. 100 90 Weight 80 Distance 70 60 50 40 30 20 10 1 2 3 4 5 6 Weight (kg) 7 1 kg 2 kg 3 kg 4 kg 5 kg 6 kg 7 kg 150 m 140 m 120 m 90 m 70 m 50 m 30 m Line graphs can have multiple lines Bar Graphs are used to compare values. What is the most common shoe length? ___________ 27 cm What is the least common shoe length? ___________ 21, 29, 30, 31 cm How many people have shoes that are 26 cm long? ________ 2 Pie charts are also used to compare values (usually as a percentage but not always). What can you expect to spend most of your time doing at Disneyland? What can you expect to spend least of your time doing at Disneyland? Roughly what percent of Federal spending does national defense account for? ~20% Roughly what percent does our nation spend on education? ~4% Scatterplots are used to compare trends among many data points. age What do each of the dots represent? _______________ 37-43 Approximately how old are husbands of 40 yo wives?____________ 65-70 Approximately how old are wives of 70 yo hubsands?____________ 38-44 MOST ages lie within which range? ________________ For each scenario, choose which type of graph would be best to use (line, bar, pie, or scatter plot). 1. To show how eating vegetables over a 10 year period can lower cholesterol. _______________ Line graph 2. To compare the leg lengths and antennae lengths of crickets. ____________________ bar graph 3. To analyze the relationship between hours studying for a test and test scores among students. _____________ Scatter plot 4. To show the percentages of students in class that are male vs. female ________________. Pie chart 5. To compare the salaries of 4 different professions: teacher, veterinarian, software engineer, banker ________ bar graph Slope of a Line Slope tells you how one variable changes in relation to the other variable or the rate of change. A straight line on a graph is linear or has constant speed. A nonlinear line illustrates increasing or decreasing speed Calculating Slope Rise Divided by Run Slope = y (distance) Rise Run x (time) OR… Calculating Slope y2 - y1 SLOPE = x2 - x1