Author: Biology Junction Team

Graphing Practice

Graphing Practice

Introduction

  • Graphing is an important procedure used by scientists to display the data that is collected during a controlled experiment
  • Line graphs must be constructed correctly to accurately portray the data collected
  • Many times the wrong construction of a graph detracts from the acceptance of an individual’s hypothesis
  • A graph contains five major parts:
    a. Title
    b. The independent variable
    c. The dependent variable
    d. The scales for each variable
    e. A legend
  • The title: depicts what the graph is about. By reading the title, the reader should get an idea about the graph. It should be a concise statement placed above the graph.
  • The Independent Variable: is the variable that can be controlled by the experimenter. It usually includes time (dates, minutes, hours), depth (feet, meters), temperature (Celsius). This variable is placed on the X axis (horizontal axis).
  • The Dependent Variable: is the variable that is directly affected by the independent variable. It is the result of what happens because of the independent variable. Example: How many oxygen bubbles are produced by a plant located five meters below the surface of the water? The oxygen bubbles are dependent on the depth of the water. This variable is placed on the Y-axis or vertical axis.
  • The Scales for each Variable: In constructing a graph one needs to know where to plot the points representing the data. In order to do this a scale must be employed to include all the data points. This must also take up a conservative amount of space. It is not suggested to have a run on scale making the graph too hard to manage. The scales should start with 0 and climb based on intervals such as: multiples of 2, 5, 10, 20, 25, 50, or 100. The scale of numbers will be dictated by your data values.
  • The Legend: is a short descriptive narrative concerning the graph’s data. It should be short and concise and placed under the graph.
  • The Mean for a group of variables: To determine the mean for a group of variables, divide the sum of the variables by the total number of variables to get an average.
  • The median for a group of variables: To determine median or “middle” for an even number of values, put the values in ascending order and take the average of the two middle values.    e.g.    2, 3, 4, 5, 9, 10     Add 4+5 (2 middle values) and divide by 2 to get 4.5
  • The mode for a group of variables: The mode for a group of values is the number that occurs most frequently.     e.g.   2, 5,  8, 2,  6,  11    The number 2 is the mode because it occurred most often (twice)  

Procedure 1:
Using the following data, answer the questions below and then construct a line graph.

 

Depth in meters Number of Bubbles / minute Plant A Number of Bubbles / minute Plant B
2 29 21
5 36 27
10 45 40
16 32 50
25 20 34
30 10 20

 

 

1. What is the dependent variable and why?  

2. What is the independent variable and why?

3. What title would you give the graph? .

4. What are the mean, median, and mode of all 3 columns of data? 

a). Depth :                      Mean____________Median__________Mode________ 

b). Bubble Plant A.:        Mean ____________Median_________Mode________ 

c). Bubbles Plant B:        Mean ____________Median_________Mode________

Graph Title: _________________________________________________________

Legend: ______________________________________________________________ 

Procedure 2:
Diabetes is a disease affecting the insulin producing glands of the pancreas. If there is not enough insulin being produced by these cells, the amount of glucose in the blood will remain high. A blood glucose level above 140 for an extended period of time is not considered normal. This disease, if not brought under control, can lead to severe complications and even death. 

Answer the following questions concerning the data below and then graph it.  

 

Time After Eating hours Glucose mg /dL of Blood Person A Glucose mg /dL of Blood Person B
0.5 170 180
1 155 195
1.5 140 230
2 135 245
2.5 140 235
3 135 225
4 130 200

 

 1. What is the dependent variable and why?

2. What is the independent variable and why?

3. What title would you give the graph?

4. Which, if any, of the above individuals (A or B) has diabetes? 

5. What data do you have to support your hypothesis? 

6. If the time period were extended to 6 hours, what would the expected blood glucose level for Person B? 

Title: ________________________________________________________________

Legend: ______________________________________________________________

Summary:
1. What conclusions can be determined from the data in graph 1?

2. What conclusions can be determined from the data in graph 2?

3. Can the data in each of these graphs be used to construct other types of graphs?

4. If so, what other graph types can be constructed?

 
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Graph Examples

Examples of Graphs

LINE GRAPHS

Line Graph title

A line graph is most useful in displaying data or information that changes continuously over time. The example below shows the changes in the temperature over a week in January. Notice that the title of the graph is “Average Daily Temperature for January 1-7 in degrees Fahrenheit”.

To the left is a table that shows the date in one column and the corresponding temperature in the second column. The line graph on the right shows the degrees of temperature going up the vertical axis (up and down numbers on the left of the graph) and the days of the week on the horizontal axis (going sideways from left to right). The points for the temperature for each day are connected by a line – thus the graph is a line graph.

Average Daily Temperature for January 1-7 in Degrees Fahrenheit

Date
Temperature
1 10
2 25
3 30
4 42
5 23
6 25
7 40
Line Graoh of Average Temperatures

 

Bar Graph Animated title

BAR GRAPHS

Bar graphs are an excellent way to show results that are one time, that aren’t continuous – especially samplings such as surveys, inventories, etc. Below is a typical survey asking students about their favorite after school activity. Notice that in this graph each column is labeled – it is also possible to label the category to the left of the bar. In this case, the numbers for each category are across the bottom of the chart.

A bar chart is marked off with a series of lines called grid lines. These lines typically mark off a numerical point in the series of numbers on the axis or line. In this case, each grid line going up and down marks a multiple of 20 as the graph is divided.  More gridlines can make it easier to be exact with the amounts being shown on the bar graph, but too many can make it confusing.  Notice that for data that does not fall evenly on a multiple of 20, the bar is in between two grid lines.  Bar graphs are useful to get an overall idea of trends in responses – which categories get many versus few responses.

Favorite Student After School Activity

Activity Number
Visit W/Friends 175
Talk on Phone 168
Play Sports 120
Earn Money 120
Use Computers 65
Bar Graph

Circle Pie Graph Title

CIRCLE/PIE GRAPHS

Circle or pie graphs are particularly good illustrations when considering how many parts of a whole are inception. In the table below both the number of hours in a whole day devoted to certain activities is listed as well as the percent of time for each of these activities. The pie chart is then divided very much as a baker’s pie would be into slices that represent the proportional amounts of time spent on each activity.

To the right of the pie chart is a legend that tells which color stands for which category. In addition, the percents are also near the pie slice that stands for that particular amount of time spent.

Percent of Hours of a Day Spent on Activities

ACTIVITY HOURS PERCENT OF DAY
Sleep 6 25
School 6 25
Job 4 17
Entertainment 4 17
Meals 2 8
Homework 2 8

 

 

Pie Graph of Day's Activities