Name: ______Date: ______Period: ______
Creating Data Tables, Graphs, & Variable Identification Review
Objectives
To create data tables that present measurements in a logical, organized format.
To select the appropriate form of graph to visually display collected data.
To correctly identify independent variables, dependent variables, control groups, and constants.
Background Information
Graphs serve a specific purpose in science. If well-constructed, a graph is one way a scientist can visually share data and/or trends with other members of the scientific community. Transforming numbers into a meaningful “picture” is challenging. Graphs are constructed so that someone who has not done an experiment can understand their meaning.
Data Tables vs. Graphs
These are not the same thing, although they are often mistaken for one another. A data table summarizes the qualitative/quantitative data collected during the experiment, and is constructed using columns and rows. A graph is a visual representation of data, and should emphasize trends and/or patterns in this data.
Types of Graphs: Sketch the most commonly used graph types in science in the boxes provided below.
1. Line Graphs 2. Bar Graph 3. Pie Chart 4. Scatter Plot
Directions: The following table summarizes the steps for graph construction.
Step / What To Do / How To Do It1 / Identify Variables / Independent Variable (manipulated and changed by the experimenter)
§ Goes on the x-axis
§ Should be on the left side of a data table.
Dependent Variable (measured by experimenter; responds to changes of indep. variable)
§ Goes on the y-axis (vertical)
§ Should be on the right side of a data table.
2 / Decide on Graph Type / Line Graph: shows a change in one or more variables over time
Bar Graph: compares variables according to one characteristic
Pie Chart: commonly used to display percentages and color coded
Scatter Plot: shows how much one variable is affected by another (correlation)
3 / Determine Ranges / Subtract the lowest data value from the highest data value.
Do each variable separately.
4 / Determine Scale / Determine a scale (the numerical value for each square) that best fits the range of each variable. Spread the graph to use MOST of the available space and entire page
5 / Axis Labels / Label each axis with a description. Include units in parentheses-ie. Mass (g)
6 / Plot Data Points / Plot each data value on the graph with a dot.
This allows you to observe the general outline of the graph if unsure as to graph type.
7 / Draw the Graph / Line Graph: connect the dots (zig-zag; show the ups and down)
Bar Graph: draw a rectangle for each data point; consider use of color
Scatter Plot: draw the line of best fit (linear, exponential, etc.); do NOT connect the dots
8 / Title Graph / Your title should clearly explain what the graph is about.
Graphs are referred to as Figures in the scientific community, and are numbered (Figure 1).
9 / Key/Legend / If your graph has more than one set of data, provide a "key" to identify the different lines.
Practice Problems
A scientist measures changes in water temperature as increasing amounts of calcium chloride are added to water. 6 Beakers are filled with 180 mL of water each. 0 g of calcium chloride is added to the water in Beaker 1 (control), 10 g to Beaker 2, 20 g to Beaker 3, 30 g to Beaker 4, 40 g to Beaker 5, and 50 g to Beaker 6. Each beaker contains 180 mL of water at a starting temperature of 21.0 °C. She measures the temperature of each beaker after 2 minutes of mixing the calcium chloride and stirring, and obtain the following readings: 21.0 °C for Beaker 1, 29.4 °C for Beaker 2, 35.0 °C for Beaker 3, 38.0 °C for Beaker 4, 40.0 °C for Beaker 5, and 41.0 °C for Beaker 6.
1. Construct a data table that displays the mass of calcium chloride added and the change in water temperature.
2. Explain why a data table is an improvement over the lists of mass and temperature data in the paragraph above.
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3. What is the independent (manipulated) variable? ______
4. What is the dependent (measured; responding) variable? ______
5. On a sheet of graph paper, create a graph of the above data. Orient the graph paper horizontally (landscape orientation). Be sure your graph fills up ½ a sheet of graph paper. Staple to this worksheet.
6. You water three sunflower plants with salt water. Each plant receives a different concentration of salt solutions. A fourth plant receives pure water. After a two week period, the height of each plant is measured.
(a.) Identify the independent variable: ______
(b.) Identify the dependent variable: ______
(c.) Identify the control group: ______
(d.) Identify two variables to hold constant: ______
7. A student wanted to test how the mass of a paper airplane affected the distance it would fly. Paper clips were
added before each test flight. As each paper clip was added, the plane was tested to see how far it would fly.
(a.) Identify the independent variable: ______
(b.) Identify the dependent variable: ______
(c.) Identify the control group: ______
(d.) Identify two variables to hold constant: ______