Standard 1: Experimental Design Your Goal!: Is able to formulate a testable question and hypothesis, with a possible explanation (If… then…) and includes the independent and dependent variables in the statement. Identifies the components, like independent variable, dependent variable, controls and constants and explains their importance to the design of a valid experiment. Interpret or predict the outcome based on information provided in a graph.

Standard 1: Experimental Design Scientific Method Science uses a series of steps called the scientific method to carry out a scientific investigation. The Scientific Method is a series of steps or techniques that are used to organize and acquire knowledge

Scientific Method 2) Identify a Question about a problem 1) Make an Observation 2) Identify a Question about a problem 3) Form a Hypothesis about the problem (if…then…) 4) Design an Experiment to TEST the hypothesis 5) Collect Data 6) Form a Conclusion

Observations See Smell Taste Hear Feel Gathered through your senses A scientist notices things in their natural world Ex: An example of an observation might be noticing that many salamanders near a pond have curved, not straight, tails See Smell Taste Hear Feel

2. Questions/Research From your observations there will be questions you don’t know. Ex. Why do salamanders near a pond have curved tails instead of straight tails?

3. Hypothesis A suggested solution to a problem. Must be testable Should be written as If…Then… statements Predicts an outcome An example of a hypothesis might be that the salamanders have curved tails due to a pollutant in the moist soil where they live. Ex. If salamanders are found near pollutants, then they are more likely to have curly tails.

Variable – factor in the experiment that is being tested 4. Experimentation- A procedure to test the hypothesis Variable – factor in the experiment that is being tested A good or “valid” experiment will only have ONE tested variable!

20 13 May be quantitative (numbers) or qualitative (descriptions) 5. Analyze the data- Results of the experiment: May be quantitative (numbers) or qualitative (descriptions) Must be organized Can be organized into charts, tables, or graphs For example: There were 20 curly tailed salamanders, and 13 tailed salamanders in area 1 20 13

6. Conclusion- The answer to the hypothesis based on the data obtained from the experiment. Did the data prove or disprove the experiment? For example: Did the pollution cause the straight tailed salamanders to be curly tailed? My data showed that there was a larger population of curly-tailed salamanders than straight tailed salamanders. I believe this demonstrates that……

Designing a Controlled Experiment It is important for experiments to have a specific, controlled procedure- why do you think this is? 1. The factors in an experiment that can be changed are called variables. Independent Variable: The variable that is changed or manipulated in the beginning Dependent Variable: The variable that is observed or measured during or at the end Constants: The variables that stay the same in the experiment. Why do you think it’s important to have things that are the same?

Designing a Controlled Experiment A controlled experiment works with one variable at a time. All other variables should be unchanged or “controlled”. If several variables were changed at the same time, the scientist would not know which variable was responsible for the observed results!

Designing a Controlled Experiment control group An experiment is based on the comparison between a __________________ with an ___________________________________________. experimental group A control group is a group that you use in the experiment as a comparison. It does not get any special treatment. (boring group) An experimental group is the group that receives the treatment, or the changed variable. a) These two groups are identical except for one factor. b) The control group serves as the comparison. It is the same as the experiment group, except that the one variable that is being tested is removed. c) The experimental group shows the effect of the variable that is being tested.

Word Bank:. Dependent Variable Control Group Constants Word Bank: Dependent Variable Control Group Constants Independent Variable Experimental Group The factor that is changed or manipulated (before you begin the experiment) is known as the _______________________________ The group that gets the special treatment is the _____________________________. The factor that is measured or observed (during or at the end of the experiment) is called the _______________________________ The group that doesn’t get any special treatment. The group that is used as a comparison is known as the _____________________________. All of the variables you could change but don’t (so they all remain constant) are called ___________________________________________ Independent variable Experimental group dependent variable control group Constants/controlled 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. On one route, you will take the route home that is the state certified route which is determined the fastest.

Word Bank:. Dependent Variable Control Group Constants Word Bank: Dependent Variable Control Group Constants Independent Variable Experimental Group Varying the route is the:

Word Bank:. Dependent Variable Control Group Constants Word Bank: Dependent Variable Control Group Constants Independent Variable Experimental Group Varying the route is the: independent variable

Word Bank:. Dependent Variable Control Group Constants Word Bank: Dependent Variable Control Group Constants Independent Variable Experimental Group Varying the route is the: independent variable The time it takes is the:

Word Bank:. Dependent Variable Control Group Constants Word Bank: Dependent Variable Control Group Constants Independent Variable Experimental Group Varying the route is the: independent variable The time it takes is the: dependent variable

Word Bank:. Dependent Variable Control Group Constants Word Bank: Dependent Variable Control Group Constants Independent Variable Experimental Group Varying the route is the: independent variable The time it takes is the: dependent variable Keeping the same walker, leaving at the same time of day, having the same amount of books in the book bag, and walking on a sunny day are all:

Word Bank:. Dependent Variable Control Group Constants Word Bank: Dependent Variable Control Group Constants Independent Variable Experimental Group Varying the route is the: independent variable The time it takes is the: dependent variable Keeping the same walker, leaving at the same time of day, having the same amount of books in the book bag, and walking on a sunny day are all: controlled variables/constants. You taking the state certified route is the:

Word Bank:. Dependent Variable Control Group Constants Word Bank: Dependent Variable Control Group Constants Independent Variable Experimental Group Varying the route is the: independent variable The time it takes is the: dependent variable Keeping the same walker, leaving at the same time of day, having the same amount of books in the book bag, and walking on a sunny day are all: controlled variables/constants. You taking the state certified route is the: control group All of the other routes you took were part of the:

Word Bank:. Dependent Variable Control Group Constants Word Bank: Dependent Variable Control Group Constants Independent Variable Experimental Group Varying the route is the: independent variable The time it takes is the: dependent variable Keeping the same walker, leaving at the same time of day, having the same amount of books in the book bag, and walking on a sunny day are all: controlled variables/constants. You taking the state certified route is the: control group. All of the other routes you took were part of the: experimental group

After your conclusion, are you done? How many times should we do the experiment? Many times! It is important to keep everything controlled to ensure the results are accurate. In order to verify the results, experiments must be retested.

What’s the difference between law and theory? Theory- unifying explanation for a broad range of information. based upon a considerable amount of evidence uses many observations and has lots of experimental proof can be applied to unrelated facts and new relationships flexible enough to be modified if new data/ proof introduced theories cannot be proven- they can only be disproven Examples of Theories: Cell Theory Germ Theory Theory of Evolution

stands the test of time, often without challenge Law stands the test of time, often without challenge experimentally proven over and over can create true predictions for different situations has uniformity and is universal Examples of Laws: 1st Law of Thermodynamics Newton’s Laws of Motion Newton’s Laws of Gravitation

Review What is an independent variable? What is a dependent variable? Why are constant variables important? Can there be more than one IV? DV? Control? Can there be more than one constant variable?

Why is it important to have a large sample size in any experiment? Analysis Questions Why is it important to have a large sample size in any experiment? It is important to test a large sample in order to get a true picture of the results of the experiment. If the sample size is too small, an inaccurate conclusion may be reached. Results obtained by testing a large number of individuals would be much more accurate than if only a few individuals had been tested.

Why is it important to repeat the experiment many times? Analysis Questions Why is it important to repeat the experiment many times? Experiments should be repeated to see if the same results are obtained each time. This gives validity to the test results.

Analysis Questions What is the importance of the control? The control shows what will happen when the experimental factor is omitted. Without the control, there would be no basis for comparison and you would not know how the experimental factor affected the results.

How is a theory different than a hypothesis? Analysis Questions How is a theory different than a hypothesis? A hypothesis is an “educated guess” that is testable through observations and experimentation. A theory is a broad statement of what is believed to be true based on many experiments and considerable amounts of data.

Analysis Questions Why is it so important that a scientist accurately describes the procedure used in the experiment? It allows other scientists to repeat the experiment and verify the results.

Analysis Questions What is the difference between the independent and the dependent variables in an experiment? The independent variable is the variable that is deliberately changed by the scientist. The dependent variable is the one observed during the experiment. The dependent variable is the data we collect during the experiment.

Analysis Questions In a “controlled experiment”, why must all of the variables, except one, be kept constant throughout the experiment? If several variables were changed at the same time, the scientist would not know which variable was responsible for the observed results.

The following slides are for review and practice!

Designing a Controlled Experiment 1. The factors in an experiment that can be changed are called variables. Independent Variable: The variable that is changed or manipulated in the beginning Dependent Variable: The variable that is observed or measured during or at the end Constants: The variables that stay the same in the experiment A controlled experiment works with one variable at a time. All other variables should be unchanged or “controlled”. (If several variables were changed at the same time, the scientist would not know which variable was responsible for the observed results!) control group 3. An experiment is based on the comparison between a __________________ with an ___________________________________________. Experimental group a) These two groups are identical except for one factor. b) The control group serves as the comparison. It is the same as the experiment group, except that the one variable that is being tested is removed. c) The experimental group shows the effect of the variable that is being tested. A control group is a group that you use in the experiment as a comparison. Does not get any special treatment. (boring group) An experimental group is the group that receives the treatment.

Example: In order to test the effectiveness of a new vaccine, 50 volunteers are selected and divided into two groups. One group will be the control group and the other will be the experimental group. Both groups are given a pill to take that is identical in size, shape, color and texture. All of the volunteers are woman between the ages of 25 and 30. Even though the volunteers are given identical looking pills, the control group will not actually receive the vaccine. 1. Describe the control group. --   2. Describe the experimental group. -- 3. What variables are kept constant? -- 4. What is the independent variable? ---- 5. What is the dependent variable? - The group that will receive the vaccine. The size, shape, color, and texture of the pill. And the volunteers are all the same. Whether or not the pill contains the vaccine. The observed health of the people taking the pill.

Practice Problem: State your hypothesis: Possible answer: You want to determine the effects of a certain fertilizer on the growth of orchids grown in a greenhouse. Materials that are available to you include: greenhouse, 100 orchid plants, water, and types of fertilizer. You want to know what orchids will grow tallest with either using Scotts brand fertilizer, Miracle Gro fertilizer, or Schultz brand fertilizer. How will you design an experiment to test different types of fertilizer? State your hypothesis: Possible answer: If different brands of fertilizer are used, then the miracle gro fertilizer will produce the tallest orchids.

How will you set up a controlled experiment? Here is one possibility: The 100 plants will be divided into 4 groups as follows:   The plants will be given 100 mL of tap water once a week. They will all be kept at the same temperature and proximity to light. Also all plants will get the same amount of soil/fertilizer. Over a period of a month, the plants will be measured to see which ones grew the tallest. Group 1: 25 plants will planted with regular soil. Group 2: 25 plants will use Scotts brand fertilizer. Group 3: 25 plants will use Miracle Gro fertilizer. Group 4: 25 plants will use Schultz fertilizer.

Control Group Experimental Group What is the control group in this experiment? The control group consists of the 25 plants that are planted in regular soil. What is the experimental group in this experiment? The experimental group consists of the 75 plants that are receiving the different brands of fertilizer

What variables must be kept constant in this experiment? In a “controlled experiment”, all variables must be kept constant except the one variable that is being changed. What variables must be kept constant in this experiment? All plants must receive the same amount and type of water once a week. All plants are grown in pots of equal size. All plants are grown at the same temperature. All plants receive the same amount of sunlight. All plants receive the same amount of soil/fertilizer. What is the Independent Variable? The type of fertilizer. What is the Dependent Variable? The height of the orchids.

Is your hypothesis supported or disproved by these results? After one month of measuring the orchids, the following data is obtained: Group 1 (Control Group): Grew to an average height of 15 cm. Group 2 (Scotts.): Grew to an average height of 35 cm. Group 3 (Miracle Gro.): Grew to an average height of 28 cm. Group 4 (Schultz): Grew to an average height of 10 cm. Is your hypothesis supported or disproved by these results? We hypothesized that the orchids would grow best with Miracle Gro fertilizer. The results do not support this. The results disprove our hypothesis.

What is your conclusion based on these results? After one month of measuring the orchids, the following data is obtained: Group 1 (Control Group): Grew to an average height of 15 cm. Group 2 (Scotts): Grew to an average height of 35 cm. Group 3 (Miracle Gro): Grew to an average height of 28 cm. Group 4 (Schultz.): Grew to an average height of 10 cm. What is your conclusion based on these results? Orchids grow best with Scotts brand of fertilizer. With using Miracle Gro or Schultz fertilizer, plant growth is inhibited.