Experimental Design Chapter 1 1 Define the Problem

Experimental Design Chapter 1

1 Define the Problem What is it you want to find out? l Sometimes called the Purpose or Question l l What are some problems scientists work on today?

2 Research l Gather as much information as possible before experimenting l Sometimes called collecting information

3 Form a Hypothesis l Predict the outcome of your experimentation l Sometimes called an educated guess l Many times hypotheses are stated in the “If…… then…. . ” format

4 Experiment Develop a procedure to test the hypothesis. l Change only one variable at a time and all other things as constants. l Independent variable – the thing you change. l Sometimes called test the hypothesis l

5 Analyze the Data l Record the results of your experiment using charts, graphs, and taking notes l Sometimes called analysis or conclusions

6 Conclusion l Compare the hypothesis to the experiment’s conclusion and publish your results for others to see l Sometimes called communicate the results l Paul Revere Hates Eggs And Cheese

l l l l The Strange Case of Beri In 1887 a strange nerve disease attacked the people in the Dutch East Indies. The disease was beri. Symptoms of the disease included weakness and loss of appetite, victims often died of heart failure. Scientists thought the disease might be caused by bacteria. They injected chickens with bacteria from the blood of patients with beri. The injected chickens became sick. However, so did a group of chickens that were not injected with bacteria. One of the scientists, Dr. Eijkman, noticed something. Before the experiment, all the chickens had eaten whole-grain rice, but during the experiment, the chickens were fed polished rice. Dr. Eijkman researched this interesting case. he found that polished rice lacked thiamine, a vitamin necessary for good health. 1. State the Problem 2. What was the hypothesis? 3. How was the hypothesis tested? 4. Should the hypothesis be supported or rejected based on the experiment? 5. What should be the new hypothesis?

l l l l How Penicillin Was Discovered In 1928, Sir Alexander Fleming was studying Staphylococcus bacteria growing in culture dishes. He noticed that a mold called Penicillium was also growing in some of the dishes. A clear area 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 areas were present. Fleming hypothesized that the mold must be producing a chemical 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 nutrient broth solution. This solution contained all the materials 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 mold had grown to a culture of bacteria. He observed that the bacteria died. 6. Identify the problem. 7. What was Fleming's hypothesis? 8. How was the hypothesis tested? 9. Should the hypothesis be supported or rejected based on the experiment? 10. This experiment led to the development of what major medical advancement?

When Experiments are Testing for something they have …. . l Independent variable (I. V. )- the factor (or variable) that gets changed on purpose in an experiment while all others remain constant. l I. V. – I changed it myself

Dependent Variable l The factors (or variables) that get changed as a result of the independent variable in an experiment The thing you measure l It depends or changes because of the I. V. l

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

Control l The group that has no variable acting upon it so that it can be compared with the results of the experiment l In drug tests, this group is given sugar pills (placebos) instead of the medicine. They are told it is medicine.

Types of Data l Quantitative – has numbers, obtained by counting, measuring. l Qualitative – descriptions that do not use numbers, including colors, tastes, smells, sound or textures

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