THE SCIENTIFIC METHOD

I. Observations An observation is a description of an object or event by using one of the 5 senses. It is 100% true statement; a fact. For example: The grass is wet.

II. Inferences In science, making an inference is when a conclusion is drawn based on information that may not be complete. You infer something based on factual data. Example of Inferences: 1. The grass is wet (factual information) because it rained (inference). 2. The grass is wet (factual information) because the sprinkler was on (inference).

III. Hypothesis IF, THEN, BECAUSE! A hypothesis is an educated guess that can be tested to prove or disprove the hypothesis. A hypothesis is a suggested answer to a problem WITHOUT the support of data. A hypothesis is made BEFORE the experiment is performed. A hypothesis is always written as: IF, THEN, BECAUSE!

E. For example: IF it rained outside, THEN the grass will still be wet, BECAUSE the sun didn’t dry off the water.

IV. Putting it All Together: Observation: The grass is wet. Inference: The grass is wet because it rained outside. Hypothesis: If it rained outside, then the grass will still be wet because the sun didn’t dry off the water.

V. What is a theory? 1. Big Bang Theory 2. Global Warming Theory A theory is an explanation made with the support of data from an experiment. A theory is based on complete information but is NOT a fact. 1. Big Bang Theory 2. Global Warming Theory 3. Pangaea Theory

VI. Scientific Method The scientific methods are the ways in which scientists answer questions and solve problems. There are 6 steps to the scientific method.

VII. The 6 Steps of the Scientific Method 2 1 3 5 4 6

The 6 Steps c. Example: Some plants are taller than other plants. Make an observation. a. Use your 5 senses! b. Not all senses have to be used at the same time. c. Example: Some plants are taller than other plants.

The 6 Steps 2) Ask a question. Pose a question to try to figure out why you observed what you did. Scientists often ask a question after making many observations. c. Example: Will fertilizers increase the growth rate of plants?

The 6 Steps 3) Formulate Hypothesis, or write or develop a possible explanation for the problem. a. NOT a question, always a statement b. A hypothesis is a prediction, or an educated guess. c. Always written as: “IF…, THEN…, BECAUSE…” d. Example: If fertilizer is added to trees, then the plants will grow faster because the added nutrients will speed their growth.

The 6 Steps 4) Test Hypothesis Design a test that will support or disprove your hypothesis. The test should be repeatable (you conduct the test more than once and get the same results every time).

c. Controlled experiment: A part of your experiment that is not altered so that you can compare changes that occur in the experiment. i. Example-having 3 plants that are all the same type of plant. d. Variables are factors that CHANGE from group to group in an experiment. i. Example-changing the type of fertilizer that each plant gets.

VII. Control Groups An experiment needs to be controlled because a scientist needs to determine that the thing they are testing for actually works. A control is the standard to which everything is compared.

VIII. Experimental Groups The experimental group is the group that tests the variables. Experimental Control Cancer drug Sugar pill Cold medicine Water Fertilizer on growth of plants Sunlight on growth of plants Darkness

b. Two types of variables: 1. Independent variable is: the variable you change in the experiment 2. Dependent variable is: the variable you are measuring c. Example: You want to measure the effect of the sun on plant growth. What do you change? What do you measure? Amount of sunlight Growth of the plant

d. The effect of the INDEPENDENT VARIABLE (sun) on the DEPENDENT VARIABLE (growth of plants).

The effect of sunlight (IV) on the growth of plants (DV). e. Examples The effect of sunlight (IV) on the growth of plants (DV). The effect of cold medicine (IV) on the number of sneezes(DV). The effect of bleach(IV) on the growth of bacteria(DV). Independent Variable (IV) Dependent Variable (DV)

Group 1 Group 2 What’s DIFFERENT? 3 trees All have same volume of water and same amount of sunlight 3 trees All have same volume of water, same amount of sunlight, and same amount of fertilizer What’s DIFFERENT? The fertilizer. The fertilizer is the VARIABLE.

Group 1 Group 2 Which is the CONTROL? 3 trees All have same volume of water and same amount of sunlight 3 trees All have same volume of water, same amount of sunlight, and same amount of fertilizer Which is the CONTROL? A control is the basis for comparison. GROUP 1 is the control because to find out if the fertilizer worked, you need to compare it with something that doesn’t have fertilizer.

Fertilizer is the VARIABLE (different). Control Experimental All have same volume of water, same amount of sunlight, and same amount of fertilizer 3 trees All have same volume of water and same amount of sunlight Fertilizer is the VARIABLE (different). This is the control because it doesn’t have the VARIABLE (the fertilizer). -Fertilizer is the INDEPENDENT VARIABLE -Growth is the DEPENDENT VARIABLE This is the experimental group because it is why you are doing the experiment.

The 6 Steps 5) Analyze/Interpret the results. After you have measured and recorded information, what do they mean? Did the trees with the fertilizer (experiment group) grow more than those in the control group (without the fertilizer)?

The 6 Steps 6) Draw conclusions. Look back at your hypothesis. Does your data support your hypothesis or reject it?

X. What makes a good experiment? Same Size of all Groups i. Example: 50 people in control and 50 people in the experimental ii. WHY? More or less people can alter the results of the experiment.

b.) Large Sample Size i. The large sample size reduces the possibility that the results are due to chance. c. Repeating the Experiment i. Every scientist from around the world should be able to repeat your experiment and obtain the exact same results.