The control group is exposed to the same conditions as the experimental roof, except for the variTABLE being tested. All experiments should have a control group. The control group is used to test whether the variTABLE is working, and then measure the experiments against this standard. Egg. Controls are needed to eliminate alternate explanations of experimental results. For example, suppose a researcher feeds an experimental artificial sweetener to sixty laboratory rats and observes that ten of them subsequently die. The underlying cause of death could be the sweetener itself or something unrelated.
Other variTABLEs, many of which may not be readily obvious, may interfere with the experimental design. For instance, perhaps the rats were simply not supplied with enough food or water, or the water was contaminated and undrinkTABLE, or the rats were under some psychological or physiological stress, etc. Eliminating each of these possible explanations individually would be time-consuming and difficult. Instead, the researcher can use an experimental control, separating the rats into two groups: one group that receives the sweetener and one that does not.
The two groups are kept in otherwise identical conditions, and both groups are observed in the same ways. Now, any difference in morbidity between the woo groups can be ascribed to the sweetener itself?and no other factor?with much greater confidence. 6. CONSTANTS: The constants in an experiment are all the factors that the experimenter attempts to keep the same. This is used to design the experiment, and hypothesis being tested. Putting the Scientific Method into Practice Step 1: Problem/ Question John watches his grandmother bake bread.
He asks his grandmother what makes the bread rise. She explains that yeast releases a gas as it feeds on sugar. John wonders if the amount of sugar used in the recipe will affect the size of the bread loaf? Step 2: Observation/ Research John researches the areas of baking and fermentation and tries to come up with a way to test his question. He keeps all of his information on this topic in a journal. John talks with his teacher and she gives him a Experimental Design Diagram to help him set up his investigation.
Dependent VariTABLE: The size Of the loaf Of bread Control Group: Because his grandmother always used egg of sugar in her recipe, John is going to use that amount in his control group. Constants: Other ingredients to the bread recipe, oven used, rise time, brand of ingredients, cooking time, type of pan used, air temperature and humidity where the bread was rising oven temperature, age of the yeast… Step 5: Collect and Analyze Data John comes up with a TABLE he can use to record his data. John gets all his materials together and carries out his experiment.
John examines his data and notices that his control worked the best in this experiment, but not significantly better than egg of sugar. Step 6: Conclusion John finds that egg of sugar produces the largest loaf. His hypothesis is accepted. Step 7: Communicating the Results John tells his grandmother about his findings and prepares to present his project in Science class. EXERCISE 1 . Choosing Hypotheses 2. A scientist has 12 plants. All the plants were the same kind and about the same size. He put three plants on a window sill inside a room.
He put another three plants in a closet without a light. He put another three more plants outside on the ground. He put his last three plants outside too, but covered them with paper bags that had wholes punched in them for air. All the plants were given good soil and enough water. The plants on the window sill and the plants outside in the open grew well. The plants outside in the bags turned yellow and grew badly. The plants in the closet died. Which of the following is the best hypothesis based on the facts? A) Green plants turn yellow due to disease. B) Green plants don’t live for very long. ) Green plants need light to grow. D) Green plants cannot grow inside e) Green plants grow well in closets. 3. Louis Pasteur, a famous scientist who lived over 100 years ago, made an important hypothesis about a certain germ called bacteria. He noticed that bacteria grew quickly in open jars of liquid, like chicken soup. Bacteria also grew in jars of soup that were sealed tightly so that no air could get in. However they didn’t grow in soup that was sealed tightly in a jaw, then boiled and kept sealed after it cooled. When was Pasteur correct hypothesis? ) Bacteria cannot grow In jars. B) Bacteria must have air to survive c) Bacteria only grow in chicken soup d) Bacteria can be killed by boiling. E) Bacteria can live in boiling liquids. . Errors in experiments Tell what is wrong with each of these experiments. Choose from this list: Not enough subjects Subjects were not similar. Conditions were not kept the same The experiment Was not reproduced. 1 . A gardener wanted to know if EX. fertilizer would be good for this vegeTABLE. He fertilized all his bean plants with EX. but didn’t put any fertilizer on his pepper plants.
His beans didn’t do well at all, but he got a good crop of peppers. He concluded that EX. fertilizer was no good. 2. Alice Larsen wanted to see if a new premium gasoline would give her more kilometers to the liter. She filled her car with the new gas and went on a long trip. When she figured her mileage, she discovered that she has gone 40 Km farther on this tank of gas then she went on a tanks of regular gas when she was driving around town as usual. She decided to buy the premium gas for then on to get better mileage. 3. A molding machine in a factory was not working very well.
About a third of the time, the plastic squirt guns that it was making come out with a flaw in the handle. The repair mechanic adjusted the stamping pressure. Then she ran one gun through. It came outset fine, so she figured she had solved the problem. 3. Comprehension The Strange Case of BeriBeri In 1 887 a strange nerve disease attacked the people in the Dutch East Indies. The disease was beriberi. 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 beriberi. The injected chickens became sick. However, so did a group of chickens that were not injected with bacteria. One of the scientists, Dry. Kinsman, noticed something. Before the experiment, all the chickens had eaten whole-grain rice, but during the experiment, the hickeys were fed polished rice. Dry. Kinsman researched this interesting case. He found that polished rice lacked thiamine, a vitamin necessary for good health. A) State the Problem b) What was the hypothesis? C) How was the hypothesis tested? ) Should the hypothesis be supported or rejected based On the experiment? E) What should be the new hypothesis? How Penicillin Was Discovered In 1 928, Sir Alexander Fleming was studying Staphylococcus bacteria growing in culture dishes. He noticed that a mould called Penicillin was also growing in some of the dishes. A clear area existed around the mould because all the cetera that had grown in this area had died. In the culture dishes without the mould, no clear areas were present. Fleming hypothesized that the mould 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 mould to a nutrient broth solution. This solution contained all the materials the mould needed to grow. After the mould grew, he removed it from the nutrient broth. Fleming then added the nutrient broth in which the mould had grown to a culture of bacteria. He observed that the bacteria died. F) Identify the problem. ) What was Flemings hypothesis? H) How was the hypothesis tested? I) Should the hypothesis be supported or rejected based on the experiment? ) This experiment lead to the development of what major medical advancement? 4. Identify the Controls and VariTABLEs Smithies 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, Smithies counts how many stacks of papers each group as made. Group A made 1,587 stacks, Group B made 2,113 stacks. Identify the: 1.
Control Group 2. Independent VariTABLE 3. Dependent VariTABLE 4. What should Smithies’ conclusion be? 5. How could this experiment be improved? 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 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 did of the shower. 6. What was the initial observation? Identify the- 7.
Control Group 8. Independent VariTABLE 9. Dependent VariTABLE ID. What should Homer’s conclusion be? Bart believes that mice exposed to radiowomen will become extra strong (maybe he’s been reading too much Radioactive Man). He decides to perform this experiment by placing 10 mice near a radio for 5 hours. 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 radioed mice were TABLE to push the block away. 7 UT of 10 of the other mice were TABLE to do the same.
Identify the- 11. Control Group 12. Independent VariTABLE 13. Dependent VariTABLE 14. What should Barb’s conclusion be? 15. How could Barb’s experiment be improved? Crusty was told that a certain itching powder was the newest best thing on the market; it even claims to cause 50% longer lasting itches. Interested in this product, he buys the itching powder and compares it to his usual product. One test subject (A) is sprinkled with the original itching powder, and another test subject (B) was sprinkled with the Experimental itching powder. Subject A ported having itches for 30 minutes.
Subject B reported to have itches for 45 minutes. Identify the- 16. Control Group 17. Independent VariTABLE 18. Dependent VariTABLE 19. Explain whether the data supports the advertisements claims about its product. It does Lisa is working on a science project. Her task is to answer the question: “Does Risotto (which is a commercial hair product) affect the speed of hair growth”. Her family is willing to volunteer for the experiment. 20. Describe how Lisa would perform this experiment. Identify the control group, and the independent and dependent variTABLEs in your description.
