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.
Drawing a graph …and when should I draw a line-graph? When should I draw a bar-chart…?
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:
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.)
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.
• 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
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)
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).
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
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.
5 steps in drawing a graph1. Choose simple scales.Put the dependent variable onthe ‘y-axis’ and the independent variable on the ‘x-axis’
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.
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.
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’.
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
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
The Uses of GraphsBar graphs show comparisons.
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
TAILS Teachers’s Favorite Singer T - Title A - AxisY Axis =DependentVariable X Axis = Independent Variable
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
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.
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.
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
TAILSTeachers’s Favorite Singer T – Title252015 A – Axis10 5 I – Interval 0 S – Scale
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?
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
Pie Graph a. When showing parts of a whole..i.e. percentages b. Must have a title and a legend
The Uses of GraphsCircle graphs show percentages of the whole Coconut
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
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
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
Chocolate Monday Tuesday Wednesday Thursday FridayOn what day was the least amount of chocolate milk sold? a. Monday b. Tuesday c. Thursday
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
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
OOPS! Wrong AnswerChocolate Monday Look for the smallest slice Tuesday Wednesday Thursday Friday Try Again