The Scientific Method

What is the Scientific Method? A universal standard for research. A series of steps to create and do experiments. Makes sure that your results are valid.

What are variables? Example: Effect of Sunlight Or Amount of Sunlight Example: Plant Growth Example: Amount of Water, Type of Plant, Type of Soil Independent Variable – ONE THING you are changing or testing the effect of. Dependent Variable – what you are measuring in your experiment. Controlled Variable or Constant – what you are keeping the same to make sure your results are accurate.

Step 1: Identify the Problem Ask a question. This is a problem you can solve using experiments. (IV) (DV) What is the effect of _________ on _________? How does _________ effect ____________? (IV) (DV)

Step 2: Do Your Research Make observations and research about the topic you chose. Plants require sunlight, water, carbon dioxide, and nutrient-rich soil to survive.

Step 3: Make a Hypothesis Hypothesis = educated guess. Predict a possible answer to the problem. Use research to help. DOES NOT HAVE TO BE CORRECT. BUT MUST BE TESTABLE.

Hypothesis Format Should be in an If… (IV goes here) then… (DV goes here) because… (Reason/Rationale goes here) If I grow a plant with sunlight, then it will grow taller than plants that do not receive sunlight, because plants need sunlight to perform photosynthesis.

Step 4: Develop an Experiment Create a procedure to test your hypothesis. Needs a detailed material list. Must get results that can be MEASURED.

Example: 10 plants will be grown in an area with sunlight. 10 plants will be grown in an area without sunlight. Each plant’s height will be measured every day for 30 days. Each plant will receive the same amount of soil and water.

Experiment Requirements Have a large sample size and 3 OR MORE trials. The more data you have the more accurate your results.

Experiment Requirements Have a control group. This is the group you are comparing your results to. This should be the “normal circumstances.”

Experiment Requirements Change only one variable at a time. This way you know what caused a change (if any).

Step 5: Collect/Analyze Results Collect results in tables, graphs, photographs. Summarize your results/data. With Sunlight Without Sunlight Plant 1 30 cm 5 cm Plant 2 27 cm Died Plant 3 34 cm 7 cm Plant 4 31 cm 6 cm Plant 5 32 cm

Step 6: Conclusions Accept or reject your hypothesis. List ways to improve your experiment or other ideas for future study.

Plant Experiment Conclusion Example Accept/Reject: The experiment proved my hypothesis. Plants with sunlight do grow more than plants without sunlight. Improve: One way to improve this experiment would be to do more trials and use more plants. Plan for Later: In the future, studies could be done on the effect water has on plant growth.

Limitations / Sources of Error Know that these are the common mistakes people make when doing experiments. Not enough trials. More than one Independent Variable. No constants or controlled variables. Human Error. Know how they affect the results (less accurate or no results). Know how to fix these problems (more trials, only one IV, make everything except IV constant etc.)

Step 7: Communicate Results Present your project and results to an audience of your peers.

Additional Vocabulary Observations – information you gather using your five senses. “The flower has five yellow petals.” Inferences – when you attempt to explain what you observed. “The flower has yellow petals to attract bees.” When something has been tested or done multiple times, we come up with: Theories – attempts to explain why something happens. Usually well tested and supported by many experiments and data. “The child has blue eyes because his parents have blue eyes that they passed along to their child.” Laws – says what should happen every time in a specific situation. “The child will have blue eyes if both parents have blue eyes.” Questions And Experiments LEAD TO