Name Date Hour AMERICAN GRAPH-ITTI

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1 COLLECTING DATA AMERICAN GRAPH-ITTI The purpose of all scientific investigation is to collect information. We call this scientific information data. Examples of data might include your height, shoe size, amount of rainfall in one year, the number of times each student is late to class (we really do this), etc. Data can be used to predict things like weather or earthquakes. It can be instrumental in making design improvements on technology like computers and CD s. Data can also be used in diagnosing illness of medical conditions. As scientists, you will need to be able to record information, evaluate experiments, and draw conclusions. To do all of this, you need to know how to use data tables and draw graphs, which is exactly what you are about to review. GRAPH IT 1 Now you will conduct a brief experiment in which you will collect data. Your team will be counting the number of times a person blinks in 3 minutes. You will need to record the total number of blinks every 30 seconds. Procedures: 1. Obtain the following materials: a partner, a clock or watch with a second hand, and your student sheet for recording data (see the bottom of this page). 2. Have one person find an object or image to focus their stare for three minutes. 3. A second person, the counter, should be seated so they can see the clock and the eyes of their partner. The counter will continuously count the number of blinks and record the total number every 30 seconds. 4. Continue counting for 3 minutes. 5. Each person should have the opportunity to be the blinker and counter. 6. Organize and record your data in a way that seems logical to you. Each person should record the group data on their own sheet. GRAPH IT 1 DATA Physical Science Page 1 Graphing Skillbuilder

2 Question: How does the organization of your data compare to other groups? Similarities: Differences: Discussion Notes: DATA TABLES The more data you collect during an experiment, the more problems you have keeping track of it. In order to make data from an experiment useful, you must record it in an organized manner. Scientists use data tables to organize data in columns so it is neat and readable. Data tables should always have a title. The title should clearly describe, to the reader, the data contained in the table. If not clearly labeled, the reader might not be able to understand and use the data in the table. Example: Mass of a Green Iguana Over Nine Months Variables and units provide important information about an experiment. Therefore, they are also included in a data table. The variable clearly describes what was being observed in an experiment. The unit tells the reader how the variable was measured. Some examples of variables include time, temperature, length, volume, mass, etc. The units for these examples would be seconds, degrees Celsius, meters, liters, grams, etc. The variables are written first in the data table. They are located either at the left of a row or the top of a column. The units are written in parentheses beside or below the variable to which they correspond. (months) Mass (grams) Here is an example of a data table with variables and units written correctly. Mass of a Green Iguana Over Nine Months Physical Science Page 2 Graphing Skillbuilder

3 The last piece of information recorded in a data table is the numerical values for each variable. For example: time (5, 10, 15, 20 seconds), temperature (0, 25, 50 degrees Celsius), length (1, 2, 3 meters), volume (5, 10, 15 ml), and mass (100, 200, 300 grams), etc. Here is an example of a data table with all parts correctly written. Mass of a Green Iguana Over Nine Months (months) Mass (grams) ORDERED PAIRS The numbers in a data table are organized in groups called ordered pairs. Ordered pairs are pieces of data that are directly related to each other in the experiment. In a data table, ordered pairs are located in horizontal rows (left to right) or in vertical columns (up and down). Below is an example of a data table in which two ordered pairs have been circled. The first ordered pair is (3 months, 47 grams) and the second ordered pair is (7 months, 70 grams). There are ten ordered pairs in this data table. Mass of a Green Iguana Over Nine Months (months) Mass (grams) Physical Science Page 3 Graphing Skillbuilder

4 GRAPH IT 2 Temperature of Water in Full Sun for Nine Minutes (minutes) Temperature ( o C) Using the data table above, answer the following questions. 1. What is the title? 2. What are the two variables? 3. What is the unit of the first variable? 4. What is the unit of the second variable? 5. List the ordered pairs. 6. What was the temperature of the water when the experiment began? 7. How long had the water been in the sun when it reached a temperature of 23 o C? GRAPH IT 3 Using the guidelines you have been given for constructing data tables, correctly complete each of the data tables below. Height of an Oak Tree in Centimeters Over Ten Years Height Physical Science Page 4 Graphing Skillbuilder

5 (Years) Height (Centimeters) Height of an Oak Tree in Centimeters Over Ten Years (Years) (Centimeters) Height of an Oak Tree in Centimeters Over Ten Years (Years) Height (Centimeters) CHOOSING A GRAPH A graph is a picture of information in a data table. A graph shows the relationship between all of the numbers in a data table. There are many types of graphs which can be used to display your data. Line graphs, bar graphs, and pie graphs are primary examples. The type of graph you use is determined by the type of data you collect. A line graph compares the relationship or trend between two variables. The information on a line graph is represented by data points that are connected by a line. A line graph shows the trend, what actually happens, between two variables over time. Examples of data which would be graphed using a line graph might include: the amount of time it takes water to reach a temperature of 100 o C, the mass of a green iguana over nine months, and the growth of an oak tree over time. A bar graph compares the trend of data over time and the relationship between each set of ordered pairs. The information on a bar graph is represented by thick blocks, drawn to scale. A bar graph focuses mainly on the differences between the ordered pairs in the data. For example, the amount of rainfall in four different cities, the height of individual members of a group, or the grade distribution in a class, would all be best illustrated on a bar graph. Physical Science Page 5 Graphing Skillbuilder

6 A pie graph uses a circle to display data. Each section of the graph represents a portion of the whole. When all of the portions are added together, their sum must be 100%. The focus of a pie graph is to show the relationship between the parts of a whole. Examples of data which could be shown in a pie chart would include the percentage of elements in the earth s crust, the amount of types of water found on earth, and the portion of each type of fuel used in the United States. GRAPH IT 4 Using the information about choosing a graph, determine which type of graph would best display each set of data and include a brief explanation or reason. 1. The temperature of all the science classrooms at school. 2. The number of each type of students associated with the different religious denominations compared to the total number of students at school. 3. The number of waves that reach the beach every minute for 1 hour. 4. The number of raisins in three different brands of cereal. 5. The amount of air pressure as you go up a mountain. Physical Science Page 6 Graphing Skillbuilder

7 PARTS OF A LINE GRAPH In science class, you will use a line graph most of the time because you will be comparing the relationship, trend, or pattern between two variables. All parts of a data table must be included in a graph. The same title, same variables, same units, and same data must be used. There are two axes on a two dimensional line graph, the horizontal and the vertical. The horizontal axis is also known as the x axis and runs along the bottom of the graph. The vertical axis, also called the y axis, runs up and down along the side of the graph. Each axis must be labeled with the proper variable and units. The variable that you change or manipulate is called the independent variable. The independent variable is always placed on the x axis. The name of each variable is placed along its axis and the units for each variable are in parentheses beside it. is almost always the independent variable in an experiment. The variable that changes as a result of the independent variable is called the dependent variable. The dependent variable goes on the y axis. The lines on an axis are labeled in even intervals. Intervals are the even spacing of numbers along the axis of a graph. Those intervals are determined by the range of the data. The range on a graph is the difference between the largest and the smallest numbers in the data. Each ordered pair shows the location where two lines intersect on the graph. The place where the two lines intersect is called a data point. There is a data point for each ordered pair in a data table. Plotting is the process of locating each data point on the graph. You may have seen graphs with data points connected by a line. The type of line drawn depends on the arrangement of the data points. If the pattern is clear, draw a straight or curved line that passes through each data point. Physical Science Page 7 Graphing Skillbuilder

8 Draw a best fit line or smooth curve if there is no clear pattern. This line should pass through as many data points as possible to form a smooth line that follows the general patter (not all data points may touch the line). If the points are totally scattered, do not try to create a pattern by connecting points with a line. However, be sure the data points are visible. GRAPH IT 5 Label each part of the graph pictured below Physical Science Page 8 Graphing Skillbuilder

9 LINE GRAPHS A Single line graph has only one line because it shows data for only one trial. Sometimes it is necessary to compare different data from similar trials. This produces a graph with two or more lines called a multiple line graph. There are still only two variables. However, you are comparing ordered pairs of different trials. Look at the example below. Traveling Rate of Three Boats (sec) Distance Boat A (m) Distance Boat B (m) Distance Boat C (m) In this data set, the two variables are time and distance, but there are three boats. There will be three different sets of ordered pairs. To determine the ordered pairs, you must match the independent variable data (time) with each set of dependent variable data (distance). For example, the ordered pairs for 5 seconds would be: boat A (5,3), boat B (5, 4), and boat C (5, 7). When plotting data, it is important to plot only one set of data at a time. You would begin by plotting all of the data for boat A, then draw the line and label it. Then you would plot all of the data for boat B followed by boat C. GRAPH IT 6 List the ordered pairs for each boat above in the space below. Boat A Boat B Boat C Physical Science Page 9 Graphing Skillbuilder

10 CONSTRUCTING A LINE GRAPH 1. Title your graph. 2. Label the x axis with the independent variable and its units. 3. Label the y axis with the dependent variable and its units. 4. Count the number of lines on the x axis. 5. Determine the range of the data for the independent variable (the difference between the largest and smallest numbers of the data). 6. Calculate the interval for the x axis using the following equation: range divided by the number of lines. 7. Label the x axis using the intervals you have calculated. You do not have to label every line. You can mark every two, three, four, or five lines depending on your interval. 8. Repeat steps four through seven for the dependent variable on the y axis. 9. Plot your data points using the ordered pairs in the data table. 10. Draw a smooth line connecting the data points. 11. If there is more than one set of ordered pairs for your graph, plot each set one at a time and draw your lines using different colors or notation. 12. For a multiple line graph, label each line or make a key. Physical Science Page 10 Graphing Skillbuilder

11 GRAPH IT 7 Construct a graph for each data table using the graphs provided. Total Rainfall Over the First Ten Days of January (Days) Rainfall (cm) What is the interval for each axis? X Y Physical Science Page 11 Graphing Skillbuilder

12 Height of Three Varieties of Tomato Plants Over Nine Weeks (weeks) Height of Plant A (cm) Height of Plant B (cm) Height of Plant C (cm) What is the interval for each axis? X Y How many data lines will appear on this graph? Physical Science Page 12 Graphing Skillbuilder

13 BEST FIT LINE GRAPH In a best fit line graph, the line(s) pass through many, but not all data points. Scientists use a best fit line graph to show relationships and trends that do not have to be exact. This graph has smooth continuous lines which represents a prediction for information data between known data points. The process of predicting these unknown data points within the line is called interpolation. A best fit line graph can also be used to find values that are not within the range of measured data. You can extend the line following the trend in the data. This process of estimating beyond the known data is called extrapolation. Look at the graph below. This is a best fit line because it best estimates the value of the data between the known points. To interpolate the number of bacteria at 5.5 hours, you would use the following procedure: 1. Draw a vertical line, perpendicular to the x axis, starting at 5.5 until it intersects the best fit line. Mark this point. 2. Starting at the point you marked, draw a horizontal line until you intersect the y axis. The number of bacteria at 5.5 hours is the point where your horizontal line intersects the y axis. The number of bacteria at 5.5 hours is approximately 45. The ordered pair for 5.5 hours is (5.5, 45). Physical Science Page 13 Graphing Skillbuilder

14 To extrapolate the number of bacteria at 8 hours, you would use the following procedure: 1. Extend the line to 8 hours beginning at the last known data point following the trend of the line. 2. Draw a vertical line, perpendicular to the x axis, starting at 8 until it intersects the best fit line. Mark this point. 3. Starting at the point you marked, draw a horizontal line until you intersect the y axis. The number of bacteria at 8 hours is the point where your horizontal line intersects the y axis. The number of bacteria at 8 hours is approximately 250. The ordered pair for 8 hours is (8,250). GRAPH IT 8 Practice drawing best lines in the graphs below. Physical Science Page 14 Graphing Skillbuilder

15 Using the data table below to: A. Construct a best fit graph. B. Extrapolate the number of guppies at 11 weeks. C. Interpolate the number of guppies at 6.5 weeks. Guppy Population in a Twenty Gallon Aquarium Over Ten Weeks (weeks) Guppies (number) Physical Science Page 15 Graphing Skillbuilder

16 GRAPH IT 9 Examine the following graphs and answer the questions based only on the information you can gather from them. Do not make inferences. Just stick to the facts. A student in a science class studied the effect of temperature on the growth of bacteria. The students obtained the following data. Temperature of Growth Chamber ( o C) Number of Bacterial Colonies Which graph correctly represents the data from the experiment? Physical Science Page 16 Graphing Skillbuilder

17 A study is being done on the amount of water needed to grow plants. Five small plots are given different amounts of water. After two months, the height of the plants is measured. The data are shown in the graph. What is the relationship between the variables? A. Increasing the amount of water increases the height of the plants. B. Increasing the height of the plants increases the amount of water. C. As the amount of water increases, the height of the plants also increases. D. Increasing the amount of fertilizer increases the height of the plants. Physical Science Page 17 Graphing Skillbuilder