Scientific Method

Science Is a way of learning about the natural world. Scientists use skills such as: Observing Quantitative Qualitative Inferring Predicting Classifying Modeling

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

Observations Gathered through your senses Gathered through your senses A scientist notices something in their natural world A scientist notices something in their natural world Write an example of an observation. Write an example of an observation. _________________ _______________

Observations An example of an observation might be noticing that many salamanders near a pond have curved, not straight, tails

There are two types of observations Qualitative observations are descriptions that do NOT involve numbers or measurements. Ex-The ball is round and red. Quantitative observations are NUMERICAL measurements. Ex- the mass of a book is 600g Was your example of an observation qualitative or quantitative? Types of Observations

Inferring When you explain or interpret the things you observe, you are inferring or making an inference. Based on reasoning from what you already know. What can you infer from this picture?

Hypothesis A suggested solution to the problem. Must be testable! Sometimes written as If…Then… statements IF is the Independent Variable the THEN is the Dependent Variable. Predicts an outcome

Hypothesis An example of a hypothesis might be that the salamanders have curved tails due to a pollutant in the moist soil where they live. Put this into an IF THEN statement. _____________________ __________________

Experiment Why do we do an experiment?. It is a procedure is to test the hypothesis.

Experiment Variable – factor in the experiment that is being tested

Experiment A good or “valid” experiment will only have ONE variable that changes!

Independent/Dependent The factor that is changed is known as the independent variable. This is what you are testing! The factor that is measured or observed is called the dependent variable. This is how you know if what you tested worked. 13

Controlled experiment Controlled Experiment: In a Controlled Experiment, only one factor or variable is changed at a time. Control - A standard with which to compare the results of an experiment. The variable that is changed purposely by YOU is the Independent (Manipulated) Variable.

WHAT IS THE PURPOSE OF A CONTROL? Controls are NOT being tested Controls are used for COMPARISON. How could you tell if fertilizer helps plants grow? You have to have one without fertilizer to compare to. 15

Constants All other variables must remain the same. These variables are called Constants The Dependent Variable is the factor being observed or measured

Types of groups There are two groups in a controlled experiment: The Control Group and The Experimental Group

EXAMPLE OF CONTROLS & VARIABLES 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. 18

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. 19

Data Results of the experiment May be Quantitative (numbers) or Qualitative Must be organized Can be organized into charts, tables, or graphs 20

Data: Record and Analyze Your Data Tables and graphs are often used in this step to organize the data. A Graph is a diagram that shows the relationship of one variable to another. A graph makes interpretation and analysis of data easier.

Three Basic Graph Types A Line Graph best represents “change over time” data. A Bar Graph should be used for “comparing values” measurements. A Pie Graph can clearly display percentages or “parts of a whole”.

Conclusion A Conclusion is a statement based on the results of the experiment. The conclusion may or may not support the hypothesis.

Drawing a conclusion Valid Results are those that measure what they were intended to measure. Reliable Results are those that can be repeated. If you cannot draw a conclusion from your results, you may have to try the investigation again or carry out further observations or experiments.

How to make an experiment Valid? What can we do to further increase the validity of an experiment? Two groups are required… the control & experimental groups There should be only ONE Variable. Write steps clearly, list all materials and amounts. Increase number of trials Increase number of test subjects/same size Keep constants between control group and experimental group.

Smithers thinks that a special juice will increase the productivity of workers. He creates two groups of 50 workers each and assigns each group the same task (in this case, they're supposed to staple a set of papers). Group A is given the special juice to drink while they work. Group B is not given the special juice. After an hour, Smithers counts how many stacks of papers each group has made. Group A made 1,587 stacks, Group B made 2,113 stacks. Identify the: 1. Control Group 2. Independent Variable 3. Dependent Variable 4. What should Smithers’ conclusion be? 5. How could this experiment be improved? 26

Homer notices that his shower is covered in a strange green slime. His friend Barney tells him that coconut juice will get rid of the green slime. Homer decides to check this out by spraying half of the shower with coconut juice. He sprays the other half of the shower with water. After 3 days of "treatment" there is no change in the appearance of the green slime on either side of the shower. 6. What was the initial observation? Identify the- 7. Control Group 8. Independent Variable 9. Dependent Variable 10. What should Homer's conclusion be? 27

Bart believes that mice exposed to microwaves will become extra strong. He decides to perform this experiment by placing 10 mice in a microwave for 10 seconds. He compared these 10 mice to another 10 mice that had not been exposed. His test consisted of a heavy block of wood that blocked the mouse food. he found that 8 out of 10 of the micro waved mice were able to push the block away. 7 out of 10 of the non-micro waved mice were able to do the same. Identify the- 11. Control Group 12. Independent Variable 13. Dependent Variable 14. What should Bart’s conclusion be? 15. How could Bart's experiment be improved? 28