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Graphing• Graphs are a useful tool in science.• The visual characteristics of a graph make trends in data easy to see.• One of the most valuable uses for graphs is to show data collected during an experiment. The graph shows your results.
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Drawing a graph …and when should I draw a line-graph? When should I draw a bar-chart…?
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Drawing a graphLook at the table of your results:If this column has• only certain fixed values, use a bar-chart:• a continuous range of values, use a line-graph:
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Graphing in ScienceGraph -Line Graph - Use when the IV changesTypes amount (day #, amount of fertilizer, etc) -Bar Graph - Use when the IV changes type (person name, color of flower, etc.)
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Choosing the Right Graph• Use a bar graph if you are not looking for trends (or patterns) over time; and the items (or categories) are not parts of a whole.• Use a pie chart if you need to compare differentparts of a whole, there is no time involved andthere are not too many items (or categories).• Use a line graph if you need to see how aquantity has changed over time. Line graphsenable us to find trends (or patterns) over time.
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• Make the data table into a graph• Graphs make it easier to see patterns in the data. Graphs X-axis independent variable Y-axis dependent variable
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Line Grapha. Used to show changes in dependent variable (plant growth) over time.b. Must have title, x-axis title (with units) and y-axis title (with units)c. Compare and look for trends and patterns using graphs example Growth of Plant A Over Time 6 5 Plant Height (cm) 4 3 2 1 0 5 10 15 20 25 30 35 40 45 50 55 Time (Days)
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The Uses of GraphsLine graphs show changes over time or the change of one variable (responding variable) due to the change of another variable (manipulated variable).
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Line Graph• A line graph is used to show change over time.• Its clear to see how things are going by the rises and falls a line graph shows. Chocolate MIlk Sold 120 100 80 Amount Sold 60 40 20 0 Monday Tuesday Wednesday Thursday Friday Day Chocolate
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5 steps in drawing a graph1. Choose simple scales.For example:1 large square = 1 newton (1 N)or1 large square = 2 N, or 5 N, or 10 NBut never choose an awkward scale,like 1 square = 3 N or 7 NChoose a scale that will make your graphuse most of the sheet of paper.
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5 steps in drawing a graph1. Choose simple scales.Put the dependent variable onthe ‘y-axis’ and the independent variable on the ‘x-axis’
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5 steps in drawing a graph2. Plot the points neatly.To mark the points we usually use an X x x xUsually you need 5 or xmore points for the graph. x xRe-check each one before your next step.
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5 steps in drawing a graph3. If the points form a straight line……draw the best straight line through them x x x x x xCheck that it looks the best straight line.
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5 steps in drawing a graph4. If the points form a curve……draw a free-hand curve of best fitDo not join the points like a ‘dot-to-dot’.
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5 steps in drawing a graphIn summary:1. Choose good scales, with the dependent variable on the y-axis2. Plot the points carefully3. Draw a line of best fit using a ruler for a straight line graph,4. or draw free-hand for a curved graph
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Bar Grapha. Use it when a set of measurements can be split into discrete and comparable groupsb. To show the relative change between these groups.c. Must have titles and legend Average Plant Growth over 50 Days 6 Average Growth in Centimeters 5 Plant A (Control) 4 Plant B (F er- tilizer 3 Added) Plant C (Compost 2 Added) 1 0 Plant A Plant B Plant C
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The Uses of GraphsBar graphs show comparisons.
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Bar Graph• A bar graph is used to show relationships between groups.• The two items being compared do not need to affect each other.• Its a fast way to show big differences. Notice how easy it is to read a bar graph. Chocolate Milk Sold 120 112 100 80 76 Amount Sold 72 60 53 40 33 20 0 Monday Tuesday Wednesday Thursday Friday Monday Tuesday Wednesday Thursday Day Friday
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TAILS Teachers’s Favorite Singer T - Title A - AxisY Axis =DependentVariable X Axis = Independent Variable
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TAILS Teachers’s Favorite SingerDecide on an appropriatescale for each axis. T - TitleChoose a scale that lets A – Axisyou make the graph aslarge as possible for yourpaper and data S – Scale
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How to determine scaleFavorite Number ofSinger Teachers • Scale is determinedToby Keith 22 by your highest &Madonna 15 lowest number.Elvis 11 • In this case yourSting 5 scale would be fromSinatra 2 2 – 22.
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How to determine IntervalsFavorite Number of • The interval is decidedSinger Teachers by your scale.Toby Keith 22 • In this case your scaleMadonna 15 would be from 2 – 22Elvis 11 and you want the scaleSting 5 to fit the graph.Sinatra 2 • The best interval would be to go by 5’s.
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TAILS Teachers’s Favorite SingerThe amount of space between onenumber and the next or one type T – Titleof data and the next on the graph.The interval is just as important as A – Axisthe scaleChoose an interval that lets you I – Intervalmake the graph as large aspossible for your paper and data S – Scale
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TAILSTeachers’s Favorite Singer T – Title252015 A – Axis10 5 I – Interval 0 S – Scale
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TAILS Teachers’s Favorite Singer T – Title 25 20 15 A – AxisNumber of Teachers 10 5 I – Interval 0 L – Labels LABEL Singers or your bars data points Label your Y a general do those Give the barsAxis. What label. What S – Scale numbers mean? do those words mean?
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When to use…• Bar graphs – Used to show data that are not continuous. – Allows us to compare data like amounts or frequency or categories – Allow us to make generalizations about the data – Help us see differences in data• Line Graphs – For continuous data – useful for showing trends over time
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Pie Graph a. When showing parts of a whole..i.e. percentages b. Must have a title and a legend
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The Uses of GraphsCircle graphs show percentages of the whole Coconut
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Circle Graph or Pie Graph• A circle graph is used to Chocolate Milk Sold show how a part of something relates to the whole.• This kind of graph is needed to show percentages effectively. Monday Tuesday Wednesday Thursday Friday
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Bar Graph Chocolate Milk Sold 120 The same data displayed 112 100 80 76 in 3 different types of Amount Sold 72 60 53 graphs. 40 Chocolate MIlk Sold 33 20 120 0 100 Monday Tuesday Wednesday Thursday Friday Monday Tuesday Wednesday Thursday Day 80 Friday Amount Sold Chocolate Milk Sold 60Circle (Pie) Graph 40 20 0 Monday Tuesday Wednesday Thursday Friday Monday Day Tuesday Chocolate Wednesday Thursday Friday Line Graph
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Chocolate Milk Sold 120 112 100 80 76 Amount Sold 72 60 53 40 33 20 0 Monday Tuesday Wednesday Thursday Friday Monday Tuesday Wednesday Thursday Day FridayOn what day did they sell the most chocolate milk? a. Tuesday b. Friday c. Wednesday
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Chocolate Monday Tuesday Wednesday Thursday FridayOn what day was the least amount of chocolate milk sold? a. Monday b. Tuesday c. Thursday
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Chocolate 120 100 80Amount Sold 60 40 20 0 Monday Tuesday Wednesday Thursday Friday Day ChocolateOn what day did they have a drop in chocolate milk sales? a. Thursday b. Tuesday c. Monday
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OOPS! Wrong Answer Chocolate Milk Sold 120 112 100 80 76 Look for the tallest barAmount Sold 72 60 53 40 33 Try Again 20 0 Monday Tuesday Wednesday Thursday Friday Monday Tuesday Wednesday Thursday Day Friday
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OOPS! Wrong AnswerChocolate Monday Look for the smallest slice Tuesday Wednesday Thursday Friday Try Again
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OOPS! Wrong Answer Chocolate 120 Look for the drop on the 100 80Amount Sold line 60 40 20 Try Again 0 Monday Tuesday Wednesday Thursday Friday Day Chocolate