INTRODUCTION TO LAB DESIGN AND

GRAPHING

GRAPHS and CHARTS Graphs and charts are tools used for organizing

information into visuals. They can be used to present information of data and observations that are made while conducting a lab.

A graph contains five major parts:

1. The independent variable

2. The dependent variable

3. The scales for each variable

4. A key or legend

5. A title

The independent variable: Is the variable that can be changed

by the experimenter(You). This variable is placed on the X axis (horizontal axis) when the graph is constructed.

X axis (independent variable)

The dependent variable: Is the variable that is directly affected by the

independent variable. It is the result of what you are measuring or changing. This variable is placed on the Y-axis (vertical axis) when the graph is constructed.

Y axis (dependent variable)

The Scales: Are the data next to the X and Y axis. You need to make sure how much space

you need to cover in your graph paper. Use the largest and lowest number to decide your scale.

Ex. Trials Tails Heads

1 19 17

2 24 27

3 23 26

What should be the lowest value on the x axis? Highest?What should be the lowest value on the y axis? Highest?

The key or legend:

Is a short description of the graph's data. It should be short and to the point, used when graphing more than one set of numbers on the same graph.

Ex. Tails

Heads

The title: Shows what the graph is about. By

reading the title, the reader should get an idea about the graph. It should include both the independent and dependent variables.

Ex.  Number of drops vs. penny side Change of climate over time

Number of students late to first period in four months

January February March April0

1

2

3

4

5

6

FreshmenSophomoresJuniors

Months

Num

ber

ofst

uden

ts

Controls and Variables Control= The control is the standard against

which the researcher compares the results from each treatment group (level) in the experiment. The researcher could then set one of the groups as the standard and measure the other groups against that standard.Ex. Plant with water= control

Variable: Something in an experiment that you can change and test

Ex. Plant with fertilizer

Constants Constants are the things that are kept the

same each time one of the trials in the experiment is repeated.

For example, constants could include the amount of water used, the brand of effervescent tablet used, the type of water used, and the fact that the water was not stirred. As many outside factors as possible should be kept constant in an experiment so that the researcher can be sure that any changes that occur do so because of the independent variable.

Practice: A student decided to test a new plant

fertilizer that would help his mom’s plants grow faster. He tested 4 plants. One of the plants was left without fertilizer. All the plants of were the same species and were tested for 4 weeks. Then he recorded the growth of the plants after 4 weeks.