Experimental Design Experimental Design

Chapter 1Chapter 1

1 Define the 1 Define the ProblemProblem

What is it you want to find out?What is it you want to find out?Sometimes called the Purpose or Sometimes called the Purpose or

QuestionQuestion

What are some problems scientists work What are some problems scientists work on today?on today?

2 2 ResearchResearch

Gather as much information as possible Gather as much information as possible before experimentingbefore experimenting

Sometimes called collecting informationSometimes called collecting information

3 Form a 3 Form a HypothesisHypothesis

Predict the outcome of your Predict the outcome of your experimentationexperimentation

Sometimes called an educated guessSometimes called an educated guess

Many times hypotheses are stated in the Many times hypotheses are stated in the “If…… then…..” format“If…… then…..” format

4 4 ExperimentExperiment

Develop a procedure to test the Develop a procedure to test the hypothesis. hypothesis.

Change only one variable at a time and all Change only one variable at a time and all other things as constants. other things as constants.

Independent variable – the thing you Independent variable – the thing you change.change.

Sometimes called test the hypothesisSometimes called test the hypothesis

5 5 Analyze the DataAnalyze the Data

Record the results of your experiment Record the results of your experiment using charts, graphs, and taking notesusing charts, graphs, and taking notes

Sometimes called analysis or conclusionsSometimes called analysis or conclusions

6 6 ConclusionConclusion

Compare the hypothesis to the Compare the hypothesis to the experiment’s conclusion and publish your experiment’s conclusion and publish your results for others to seeresults for others to see

Sometimes called communicate the Sometimes called communicate the resultsresults

Paul Revere Hates Eggs And CheesePaul Revere Hates Eggs And Cheese

The Strange Case of BeriBeriThe Strange Case of BeriBeri In 1887 a strange nerve disease attacked the people in the Dutch In 1887 a strange nerve disease attacked the people in the Dutch

East Indies. The disease was beriberi. Symptoms of the disease East Indies. The disease was beriberi. Symptoms of the disease included weakness and loss of appetite, victims often died of included weakness and loss of appetite, victims often died of heart failure. Scientists thought the disease might be caused by heart failure. Scientists thought the disease might be caused by bacteria. They injected chickens with bacteria from the blood of bacteria. They injected chickens with bacteria from the blood of patients with beriberi. The injected chickens became sick. patients with beriberi. The injected chickens became sick. However, so did a group of chickens that were not injected with However, so did a group of chickens that were not injected with bacteria.bacteria.

One of the scientists, Dr. Eijkman, noticed something. Before the One of the scientists, Dr. Eijkman, noticed something. Before the experiment, all the chickens had eaten whole-grain rice, but experiment, all the chickens had eaten whole-grain rice, but during the experiment, the chickens were fed polished rice. Dr. during the experiment, the chickens were fed polished rice. Dr. Eijkman researched this interesting case. he found that polished Eijkman researched this interesting case. he found that polished rice lacked thiamine, a vitamin necessary for good health. rice lacked thiamine, a vitamin necessary for good health.

1. State the Problem 1. State the Problem 2. What was the hypothesis?2. What was the hypothesis? 3. How was the hypothesis tested?3. How was the hypothesis tested? 4. Should the hypothesis be supported or rejected based on the 4. Should the hypothesis be supported or rejected based on the

experiment?experiment? 5. What should be the new hypothesis?5. What should be the new hypothesis?

How Penicillin Was DiscoveredHow Penicillin Was Discovered In 1928, Sir Alexander Fleming was studying Staphylococcus In 1928, Sir Alexander Fleming was studying Staphylococcus

bacteria growing in culture dishes. He noticed that a mold called bacteria growing in culture dishes. He noticed that a mold called Penicillium was also growing in some of the dishes. A clear area Penicillium was also growing in some of the dishes. A clear area existed around the mold because all the bacteria that had grown in existed around the mold because all the bacteria that had grown in this area had died. In the culture dishes without the mold, no clear this area had died. In the culture dishes without the mold, no clear areas were present.areas were present.

Fleming hypothesized that the mold must be producing a chemical Fleming hypothesized that the mold must be producing a chemical that killed the bacteria. He decided to isolate this substance and test that killed the bacteria. He decided to isolate this substance and test it to see if it would kill bacteria. Fleming transferred the mold to a it to see if it would kill bacteria. Fleming transferred the mold to a nutrient broth solution. This solution contained all the materials the nutrient broth solution. This solution contained all the materials the mold needed to grow. After the mold grew, he removed it from the mold needed to grow. After the mold grew, he removed it from the nutruient broth. Fleming then added the nutrient broth in which the nutruient broth. Fleming then added the nutrient broth in which the mold had grown to a culture of bacteria. He observed that the mold had grown to a culture of bacteria. He observed that the bacteria died. bacteria died.

6. Identify the problem.6. Identify the problem. 7. What was Fleming's hypothesis?7. What was Fleming's hypothesis? 8. How was the hypothesis tested?8. How was the hypothesis tested? 9. Should the hypothesis be supported or rejected based on the 9. Should the hypothesis be supported or rejected based on the

experiment?experiment? 10. This experiment led to the development of what major medical 10. This experiment led to the development of what major medical

advancement?advancement?

When Experiments are Testing for When Experiments are Testing for something they have …..something they have …..

Independent variableIndependent variable (I.V.)- the factor (or (I.V.)- the factor (or variable) that gets changed variable) that gets changed on purposeon purpose in in an experiment while an experiment while all othersall others remain remain constant. constant.

I.V. – I changed it myselfI.V. – I changed it myself

Dependent VariableDependent Variable

The factors (or variables) that get changed The factors (or variables) that get changed as a result of the independent variable in as a result of the independent variable in an experimentan experiment

The thing you measure The thing you measure It depends or changes because of the I.V. It depends or changes because of the I.V.

ConstantsConstants

The factors in an experiment that remain The factors in an experiment that remain the same. They are not changed.the same. They are not changed.

ControlControl

The group that has no variable acting The group that has no variable acting upon it so that it can be compared with the upon it so that it can be compared with the results of the experimentresults of the experiment

In drug tests, this group is given sugar pills In drug tests, this group is given sugar pills (placebos) instead of the medicine. They (placebos) instead of the medicine. They are told it is medicine. are told it is medicine.

Types of DataTypes of Data

Quantitative – has numbers, obtained by Quantitative – has numbers, obtained by counting, measuring.counting, measuring.

Qualitative – descriptions that do not use Qualitative – descriptions that do not use numbers, including colors, tastes, smells, numbers, including colors, tastes, smells, sound or texturessound or textures

Qualitative or QuantitativeQualitative or Quantitative

The floor is shiny.The floor is shiny.There are 19 students in the class.There are 19 students in the class.The walls are white.The walls are white.The board is 1 meter high and 2 meters The board is 1 meter high and 2 meters

wide.wide.