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Chapter 1, Section 2


Chapter 1, Section 2

The Scientific Process

Although you might not know it, your thinking and questioning can be the start of the scientific inquiry process. Scientific inquiry refers to the diverse ways in which scientists study the natural world and propose explanations based on the evidence they gather. If you have ever tried to figure out why a plant has wilted, then you have used scientific inquiry. Similarly, you could use scientific inquiry to find out whether there is a relationship between the air temperature and crickets’ chirping.

Posing Questions

Scientific inquiry often begins with a problem or question about an observation. In the case of the crickets, your question might be: Does the air temperature affect the chirping of crickets? Of course, questions don’t just come to you from nowhere. Instead, questions come from experiences that you have and from observations and inferences that you make. Curiosity plays a large role as well. Think of a time that you observed something unusual or unexpected. Chances are good that your curiosity sparked a number of questions.

Some questions cannot be investigated by scientific inquiry. Think about the difference between the two questions below.

The first question is a scientific question because it can be answered by making observations and gathering evidence. For example, you could measure the amount of food your cat and dog each eat during a week. In contrast, the second question has to do with personal opinions or values. Scientific inquiry cannot answer questions about personal tastes or judgments.

Developing a Hypothesis

How could you explain your observation of noisy crickets on that summer night? “Perhaps crickets chirp more when the temperature is higher,” you think. In trying to answer the question, you are in fact developing a hypothesis. A hypothesis (plural: hypotheses) is a possible explanation for a set of observations or answer to a scientific question. In this case, your hypothesis would be that cricket chirping increases at higher air temperatures.

Figure 7Developing Hypotheses A hypothesis is one possible way to explain a set of observations. A hypothesis must be testable—scientists must be able to carry out investigations to test the hypothesis. Developing Hypotheses Propose another hypothesis that could account for this boy’s observations.

In science, a hypothesis must be testable. This means that researchers must be able to carry out investigations and gather evidence that will either support or disprove the hypothesis. Many trials will be needed before a hypothesis can be accepted as true.

Reading Checkpoint

Designing an Experiment

To test your hypothesis, you will need to observe crickets at different air temperatures. All other variables , or factors that can change in an experiment, must be exactly the same. Other variables include the kind of crickets, the type of container you test them in, and the type of thermometer you use. By keeping all of these variables the same, you will know that any difference in cricket chirping must be due to temperature alone.

An experiment in which only one variable is manipulated at a time is called a controlled experiment . The one variable that is purposely changed to test a hypothesis is called the manipulated variable (also called the independent variable). In your cricket experiment, the manipulated variable is the air temperature. The factor that may change in response to the manipulated variable is called the responding variable (also called the dependent variable). The responding variable here is the number of cricket chirps.

Skills Activity

Controlling Variables

Suppose you are designing an experiment to determine whether birds eat a larger number of sunflower seeds or millet seeds. What is your manipulated variable? What is your responding variable? What other variables would you need to control?

Another aspect of a well-designed experiment is having clear operational definitions. An operational definition is a statement that describes how to measure a variable or define a term. For example, in this experiment you would need to determine what sounds will count as a single “chirp.”

Collecting and Interpreting Data

For your experiment, you need a data table in which to record your data. Data are the facts, figures, and other evidence gathered through observations. A data table is an organized way to collect and record observations. After the data have been collected, they need to be interpreted. A graph can help you interpret data. Graphs can reveal patterns or trends in data.

Figure 8A Controlled Experiment In their controlled experiment, these students are using the same kind of containers, thermometers, leaves, and crickets. The manipulated variable in this experiment is temperature. The responding variable is the number of cricket chirps per minute at each temperature. Controlling Variables What other variables must the students keep constant in this experiment?

Reading Checkpoint

Drawing Conclusions

A conclusion is a summary of what you have learned from an experiment. In drawing your conclusion, you should ask yourself whether the data support the hypothesis. You also need to consider whether you collected enough data. After reviewing the data, you decide that the evidence supports your original hypothesis. You conclude that cricket chirping does increase with temperature. It’s no wonder that you have trouble sleeping on those warm summer nights!

Scientific inquiry usually doesn’t end once a set of experiments is done. Often, a scientific inquiry raises new questions. These new questions can lead to new hypotheses and new experiments. Also, scientific inquiry is not a rigid sequence of steps. Instead, it is a process with many paths, as shown in Figure 9.


An important part of the scientific inquiry process is communicating your results. Communicating is the sharing of ideas and experimental findings with others through writing and speaking. Scientists share their ideas in many ways. For example, they give talks at scientific meetings, exchange information on the Internet, and publish articles in scientific journals. When scientists communicate their research, they describe their procedures in full detail so that other scientists can repeat their experiments.

Figure 9Scientific Inquiry There is no set path that a scientific inquiry must follow. Observations at each stage of the process may lead you to modify your hypothesis or experiment. Conclusions from one experiment often lead to new questions and experiments.

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