Question

Lab 1: Using the Scientific Method Worksheet

At a local town meeting, one of your neighbors complains that a nearby residence is killing his flowers because of the chemicals he uses to wash his cars. He claims that the soap runs into a stream that flows very close to his flower beds. As an inquiring student of science, you wonder whether soap can truly affect flower growth.

Based on the observation given to you, use the following questions to explain how you would set up your experiment and analyze your results.

1.       State your hypothesis. Remember that a hypothesis must be specific and testable. For example, stating that detergents are bad is not a good hypothesis (“Bad” is a generic term, it would be better to use a metric that is measurable).

2.       Explain how you would set up your control and treatment groups. What would be the same between the groups and what would be different? What species would you use for each group and how many plants total would you use?

3.       How would you collect your data for your experiment? What tools and units of measurement would you use? How often would you collect data and would you use the same methodology for both your treatment and control groups? Be specific in your answers.

In every experiment, there are some unintentional differences between the control and treatment groups. These are called sources of error. If these sources of error can be corrected we call them avoidable sources of error. An example of an avoidable source of error may be the amount of water provided to the plant. We can avoid this error by watering the plants in each group, the same amount at the same time of the day.

4. List some possible sources of avoidable and unavoidable error in your fertilizer experiment that were provided to you as examples.

5..       Explain the difference between a theory and a hypothesis.

6.       Explain the difference between the ‘everyday’ use of the word theory and the definition of a scientific theory.

7.       Why is it important to educate people on the true definition of “theory”?

Answer 1

5. A Hypothesis is a tentative statement which provides explanations regarding a phenomenon or event. It is widely used as a base for conducting tests and the results of the tests determine the acceptance or rejection of the hypothesis. A Theory is the scientific explanation of an observed activity or a phenomenon. It explains the observations or events that are based upon any proven hypothesis. Therefore, hypothesis forms the base for a theory.

A Hypothesis is an uncertain explanation regarding a phenomenon or event. It is widely used as a base for conducting tests and the results of the tests determine the acceptance or rejection of the hypothesis. A tentative statement takes a form like - “If X happens then Y must happen”. Hypothesis can be tested by various methods, including the direct experimentation or using certain observation skills. It is important to mention that theories, laws and facts can start from being just a hypothesis at the initial phase.

It can always be tested by experimentation after the formulation. It is generated by gathering possible evidence. Later, the investigation is carried out to test the hypothesis. It is either accepted or assumed.

A Theory is basically a system comprising of ideas through which explanations are made. A theory is based on the hypothesis. If the hypothesis is able to survive and pass all critical tests then it is eligible to be mentioned as a theory. A theory is always supported by evidence. Therefore, it is regarded to be a well confirmed type of explanation. A theory may also be used for predicting any of the future observations. One of the famous theories is Darwin’s Revolutionary Theory. Darwin derived and used the information from various fields and subjects to establish this theory.

Hypothesis and theory are related to each other but still differ in many aspects. Hypothesis is a testable proposition, whereas theory is a coherent set of propositions. Hypothesis is always testable and this property defines the very basic property of a hypothesis. On the other hand, theory is a result that is obtained by rigorous testing and investigations.

6. According to the National Academies of Sciences, "some scientific explanations are so well established that no new evidence is likely to alter them. The explanation becomes a scientific theory. In everyday language a theory means a hunch or speculation. Not so in science. In science, the word theory refers to a comprehensive explanation of an important feature of nature supported by facts gathered over time. Theories also allow scientists to make predictions about as yet unobserved phenomena".

People who don't understand this distinction sometimes dismiss ideas saying "it's just a theory" (this is very commonly used to suggest that evolution is just speculation, for example). But, when scientists speak of the theory of gravity or the theory of evolution, they don't mean that these are random untested ideas that someone came up with after too many beers.

The AAAS (American Association for the Advancement of Science), the world's largest scientific society, has this explanation of what scientists mean when they use the word "theory":

" A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on a body of facts that have been repeatedly confirmed through observation and experiment. Such fact-supported theories are not "guesses" but reliable accounts of the real world."