Scientific Method

Steps in the Scientific Method Observation Hypothesis Experiment Data Collection Conclusion Retest

An example of an observation might be noticing that many salamanders near a pond have curved, not straight, tails. The pond is located by a farmers field where pesticides are regularly sprayed on crops. Observations

Hypothesis A suggested solution to the problem. Must be testable Sometimes written as If…Then… statements Predicts an outcome

Hypothesis An example of a hypothesis : If the concentration of a pesticide is increased, then there will be a greater percentage of salamanders with curled tails.

A defined and specific procedure structured to test the hypothesis. Experiment!! A defined and specific procedure structured to test the hypothesis.

Some rules: Change one factor (variable) and observe or measures what happens. Control all other factors (referred to as ‘controlled variables’) Use a control group when possible Quantify data as much as possible. Collect qualitative data as well!

Are the controlled variables the same thing as the control group? No! Explain!

What is the Purpose of a control group? Control groups are not under testing parameters. Control groups often symbolize the normal state. They are often used for COMPARISON

Other Variables The factor that is changed is known as the independent variable (ex. We change the type of additive (pesticide or not) that we give to each individual in a test group) The factor that is measured or observed is called the dependent variable (ex. We measure the effects of the pesticide (or not) on growth/change in tail of salamander)

Example For example, suppose you want to figure out the fastest route to walk home from school. You will try several different routes and time how long it takes you to get home by each one. Since you are only interested in finding a route that is fastest for you, you will do the walking yourself.

What are the Variables in Your Experiment? Varying the route is the independent variable The time it takes is the dependent variable Keeping the same walker throughout makes the walker a control variable.

One more thing… it is best to make several trials with each independent variable.

Can be organized into charts, tables, or graphs Data Must be organized Can be organized into charts, tables, or graphs Results of the experiment May be quantitative (numbers) or qualitative

Conclusion The answer to the hypothesis based on the data obtained from the experiment

In order to verify the results, experiments must be retested.

Example: Potato Chips and Stomach Aches Researchers tested the prediction that Olestra® in potato chips causes cramps Experimental group: Olestra chips Control group: regular chips

Olestra® causes intestinal cramps. Hypothesis Olestra® causes intestinal cramps. Prediction People who eat potato chips made with Olestra will be more likely to get intestinal cramps than those who eat potato chips made without Olestra Experiment Control Group Eats regular potato chips Experimental Group Eats Olestra Results Control Group Eats regular potato chips Experimental Group Eats Olestra Conclusion Percentages are about equal. People who eat potato chips made with Olestra are just as likely to get intestinal cramps as those who eat potato chips made without Olestra. These results do not support the hypothesis. Stepped Art Fig. 1-10, p. 14

Sampling Error in Experiments Researchers experiment on subsets of a group Results may differ from results of the same experiment performed on the whole group Sampling error is a difference between results from a subset and results from the whole Small sample size increases the likelihood of sampling error in experiments