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Displaying and Analyzing DataThe best method for displaying and analyzing data isthrough the use of graphsGraphing is an important procedure used by scientists toeasily compare multiple variables.There are many types of graphs, but the three mostcommon kinds are line graphs, bar graphs, and pie charts -- In this class, we will be primarily using line graphsand bar graphs 90 80 70 60 50 E as t 40 W es t 30 N o rt h 20 10 0 1s t 2 nd 3 rd 4th Qtr Qtr Qtr Qtr
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What type of graph?• You may wonder; How do I know which type of graph to use? – Line graphs out now!!just for time graphs!!! Find are not Click Here! – Use a line graph when you have 2 quantitative (number) variables • Ex. Speed vs. engine size – Use a bar graph when you have one qualitative variable and one quantitative variable • Ex. Migration distance vs. bird species
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Creating a Graph y• Draw and label the x-axis and the y-axis -- the x-axis is the horizontal axis and the y-axis is the vertical axis8. Label what variable is on each axis -- the independent (manipulated) variable always x goes on the x-axis and the dependent (responding) Independent Variable variable always goes on the y-axis
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Creating a Graph1. Decide which intervals you will be using on each axis and write those in – Be sure that the intervals are appropriate for your graph • Ex. 1 – If your dependant variable has values ranging from 5cm to 600cm, an interval of 5cm might not be enough • Ex. 2 – If you are measuring the growth of a plant each week, you shouldn’t use meters on your graph y 75 74 73 72 71 70 69 68 67 66 65 64 x 1991 1992 1993 1994 1995 Year
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Creating a Graph1. Plot the data points that you collected on the graph.2. If the graph is a line graph, connect the points with as smooth a line as possible.3. Give your graph a title – Usually, the title of a graph is similar to the variables being manipulated and y measured. Bob’s Weight Change Over Time 75 74 73 72 71 70 69 68 67 66 65 64 x 1991 1992 1993 1994 1995 Year
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Graphical Analysis• Remember that the reason for creating graphs is to help us to better visualize what has occurred. – You should always look at your graph after you make it and consider what it is telling you • What is the general trend in the data? What is the relationship between the variables? Does it make sense? Final Questions
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Question 1• You run an experiment to test how the brand of gasoline used effects your cars gas mileage. When you graph the data: – What type of graph would you make? Bar Graph – brand is a qualitative variable, mileage is quantitative Answer – Which variable would go on the x-axis? Why?The brand would go on the x-axis because it is the independent variable Answer – Which variable would go on the y-axis? Why?The mileage would go on the y-axis because it is the dependant Answervariable
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Question 2 • You measure the height of everyone at GM and create a graph of average height for each age from 14 to 18 – What type of graph should this be? This should be a line graph because both variables are quantitative Answer – What trend do you expect to see in the data? The graph should have a positive (upward) slope. As students get older Answer you would expect their heights to increase.Remember to write out 2-5 questions aboutthe notes for class!!
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