Scientific Method

Designing an Experiment Scientist have come up with a method as how to approach and perform an experiment. This method is called the scientific method.

Scientific Method Steps Ask a question. Form a Hypothesis. Set up a controlled experiment & test. Record and analyze results. Draw a conclusion.

Asking a Question A problem must be identified that can be solved by asking a question. Something is considered a problem if a solution is not obvious. Poor example: What fertilizer is the best? Good Example:Which fertilizer, Miracle Grow or VitaGro is best for growing a particular species of roses?

Form a Hypothesis A hypothesis is a proposed scientific explanation for a set of observations. Scientists generate hypotheses using prior knowledge, logical inference, and informed imagination. Basically predict a solution and test it.

Hypothesis Examples Poor Example: I think the fertilizer will help the plants. I think that the roses will grow better with fertilizer  Good Example: If I use Miracle Grow instead of no fertilizer, then the flowers with Miracle Grow will produce more flowers compared to the one without miracle grow.

Setting Up a Controlled Experiment Experiments must contain variables, or factors that can change. Whenever possible, a hypothesis should be tested by an experiment in which only one variable is changed at a time. All other variables should be kept unchanged, or controlled, hence the name (controlled experiment).

Setting Up a Controlled Experiment Other variables in a controlled experiment include: Independent variables- the variable that is changed, sometimes called manipulated variable. Dependent variables- the variable that changes in response to the independent variable. The dependent variable is usually what is measured.

Materials Make sure that materials are very specific Poor Example : Roses, soil, water, fertilizer Good Example: 1. 150 red rose plants (same species) each 2 feet tall 2. 150 identical 5 gal buckets with 3 holes in the bottom 3. 10 bags of Home Depot brand potting soil (20 lbs.) 4. Miracle Grow fertilizer 5. VitaGrow fertilizer 6. Water 7. Graduated cylinder to measure water 8. Grow lights or green house 9. Yard stick

Procedure Your procedure should be written in such a way that any person using it could get identical results.

Procedure Examples Poor Example: 1.Plant roses, some with fertilizer, some without 2.Water roses 3.Set plants under grow light 4.Count number of flowers GoodExample: 1. Fill 150 buckets with potting soil to within one inch of the top. 2. Plant one plant in each bucket so that all of its roots are covered with potting soil. 3. Water each plant with 1 liter of tap water. 4. Divide the plants into 3 equal groups of 50 plants each, groups A, B and C

Record & Analyze Data Scientists usually keep written records of their observations, or data. Data may be recorded in two forms: Quantitative data- data expressed in numbers, obtained by counting or measuring. Qualitative data- data that is descriptive and involve characteristics that can’t be counted or measured.

Data When designing an experiment, you must decide what and how you are going to collect the data. What will you measure. When will you measure it? How will you display the data once it is collected? Be sure to write it specifically in the procedures. *Typically the independent variable comes first in the data table followed by the dependent variable.

Drawing a Conclusion Scientists use the data from an experiment to draw conclusions about the hypothesis. (Either support or reject the hypothesis) Once a conclusion has been reached, scientist will repeat the experiment to make sure that the results are the same.

Writing a Conclusion Restate your hypothesis. State if your hypothesis was correct or incorrect. Answer your problem in a complete sentence. (Always look back at your purpose (problem) to be sure you answer the right question). PROVE your answer to your problem. Use ACTUAL DATA from your experiment to support your answer. This makes you more credible. Restate your findings as a concluding thought.

Theories As evidence from numerous investigations builds up, a particular hypothesis may become so well supported that scientists consider it a theory. In science, the word theory applies to a well-tested explanation that unifies a broad range of observations.