Scientific Method

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

Observations Gathered through your senses A scientist notices something in their natural world For example, you may notice that many salamanders near a pond have curved rather than straight tails.

Hypothesis Predicts an outcome Must be testable I think the salamanders have curved tails due to a pollutant in the soil where they live. Predicts an outcome Must be testable

Experiment A procedure used to test the hypothesis. Independent variable Dependent variable Constants Control group Experimental group

Independent Variable The factor that is being changed or tested in an experiment. Example: One group of salamanders is exposed to a certain pollutant and the other group is not. The tail growth of both groups is monitored for 6 months. Each group is given the same diet and they are all the same age and species of salamander. Can you identify the independent variable?

Dependent Variable Your results! The outcome… what is being measured or observed. Example: One group of salamanders is exposed to a certain pollutant and the other group is not. The tail growth of both groups is monitored for 6 months. Each group is given the same diet and they are all the same age and species of salamander. Can you identify the dependent variable?

Constants Every factor besides the independent variable must remain the same so that you know for sure what has affected your results. You hypothesize that plants will grow taller in the sunlight. To test this, you set up two groups: one is in the sunlight and given water every day, while plants in the other group are kept in the dark without water. At the end of the experiment, plants in the first group are taller… but was it the sunlight or the water? Or both?

Constants Example: One group of salamanders is exposed to a certain pollutant and the other group is not. The tail growth of both groups is monitored for 6 months. Each group is given the same diet and they are all the same age and species of salamander. Can you identify some constants?

Control Group One group of test subjects is used for comparison. They do not get exposed to the independent variable. Example: One group of salamanders is exposed to a certain pollutant and the other group is not. The tail growth of both groups is monitored for 6 months. Each group is given the same diet and they are all the same age and species of salamander.

Experimental Group The group that is being tested on. Example: One group of salamanders is exposed to a certain pollutant and the other group is not. The tail growth of both groups is monitored for 6 months. Each group is given the same diet and they are all the same age and species of salamander.

Data Results of the experiment May be quantitative (numbers) or qualitative Example: 75% of the salamanders exposed to the pollutant developed curved tails, while only 3% of salamanders in the other group had curved tails.

Precision: all measurements or results agree with each other. Precision vs. Accuracy Precision: all measurements or results agree with each other. Accuracy: the measurement or result reflects the correct value.

Precision vs. Accuracy

Conclusion The answer to the hypothesis based on data collected from the experiment. Our data suggested that our hypothesis was correct- pollutants were causing abnormal tail shape in salamanders.

Retest In order to verify the results, experiments must be retested. How can you make an experiment more “valid”? Retest! Large sample sizes Performed by different scientists or groups

Scientific Method Identify a problem State observations about the problem Form a hypothesis Design an experiment Collect data Form a conclusion Retest