Embedded Files
Before we go any further there are a few terms you will need to be familiar with:
Exercise 2: Watch the video and fill in the blanks
In order for an experiment to be _______________, you can only change one thing at a
time, everything else in the experiment needs to stay ______________________.
Independent variable =____________________________________________________
_______________________________________________ (amount of water the plants get)
Controlled variables =
__________________________________________________________
____________________________________________ (temperature, amount of sun, place)
Dependent variable =
__________________________________________________________
_____________________________________________________ (the height of the plants)
CONTROL GROUP: In many scientific experiments the scientists use a control group.
The control is the group that serves as the standard of comparison. Controls are needed to
eliminate alternate explanations of experimental results.
For example, suppose a researcher tests a new medicine to sixty laboratory rats and
observes that ten of them die. The cause of death could be the medicine itself or something
unrelated. Other variables, many of which may not be readily obvious, may interfere with the
experimental design. Maybe these rats were not fit when the experiments started. Or the
experiment caused to much stress.
To improve the experiment the researcher can use a control group. This means separating
the rats into two groups: one group that receives the medicine 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 two groups can be ascribed to the
medicine itself—and no other factor—with much greater confidence.
Exercise 3: Identify the variables
Identify the:
1. Control Group
2. Independent Variable
3. Dependent Variable
4. What should Smithers' conclusion be?
5. How could this experiment be improved?
Smithers 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, Smithers counts how many stacks of papers each group has made. Group A made 1,587 stacks, Group B made 2,113 stacks.
6. What was the initial observation?
Identify the :
7. Control Group
8. Independent Variable
9. Dependent Variable
10. What should Homer's conclusion be?
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 side of the shower.
Identify the-
11. Control Group
12. Independent Variable
13. Dependent Variable
14. What should Bart's conclusion be?
15. How could Bart's experiment be improved?
Bart believes that mice exposed to radio waves 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 radio-waved mice were able to push the block away. 7 out of 10 of the other mice were able to do the same.
Identify the:
16. Control Group
17. Independent Variable
18. Dependent Variable
19. Explain whether the data supports the advertisements claims about its product.
Krusty 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 reported having itches for 30 minutes. Subject B reported to have itches for 45 minutes.
20. Describe how Lisa would perform this experiment. Identify the control group, and the independent and dependent variables in your description.
Lisa is working on a science project. Her task is to answer the question: "Does Rogooti (which is a commercial hair product) affect the speed of hair growth". Her family is willing to volunteer for the experiment.
Before we go any further there are a few terms you will need to be familiar with:
1. HYPOTHESIS: The hypothesis is an educated guess about the relationship between the independent and dependent variables.
2. VARIABLES: Variable is a logical set of attributes such as measurable quantities, categories such as gender, numbers, or words. Variables “vary”, can be high, or low.
3. INDEPENDENT VARIABLES: or manipulated variable, is a factor that’s intentionally varied by the experimenter. The researcher changes this variable, it is under their control. Eg. Changing temperature, water quantities, etc.
4. DEPENDENT VARIABLES: or responding variable (responds to the independent variable – “dependent” on the independent), is the factor that may change as a result of changes made in the independent variable. Eg. Plant growth, cell growth etc. Scientists cannot predict how high plants are going to grow, nor can they make them grow a certain height, they can only wait and see.
5. CONTROL GROUP: In a scientific experiment, the control is the group that serves as the standard of comparison. The control group may be a “no treatment" or an “experimenter selected” group.
The control group is exposed to the same conditions as the experimental group, except for the variable being tested. All experiments should have a control group.
The control group is used to test whether the variable is working, and then measure the experiments against this standard.
Eg. 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 variables, 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 undrinkable, 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 two 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
Google Sites
Report abuse