EXPERIMENT The experiment portion will be where a procedure is designed to test the validity of the hypothesis. In science, this systematic process is referred to as a controlled experiment. Any such experiment should have the following components: an experimental group and control group. The role of the control group is to remain unchanged, therefore serving as a basis of comparison for the experimental group. In contrast, the experimental group is going to be manipulated to assess your hypothesis. In other words, that group will receive the treatment, which allows a comparison of the results to the control group. See Figure 1.2 to examine the controls in this study on the effects of tail length on bird mating. hey witl tather Cape maies and artficialy lenghen or shorten tails by cuting a control group eu 3 Count he sesth with eggs or young on each and tathened the even hough thay successfuty delended their depiny sites Sexual selection in Euplectes progne has favored the evolution ef long tails in Figure 1.2 5. What were the two controls in the bird experiment? Pretend you are in charge of a study for a drug that is thought to lower blood pressure. Next, you have defined the two groups and populated them with individuals appropriate to the study. In addition to the difference of the drug treatment, would it be a good idea if the two groups also slept for different amounts of time, ate totally different foods, got different amounts of exercise, and had differences in alcohol and smoking habits? It is likely someone would say no to all of the above questions. 6. Why? A variable is any factor or condition that can vary. Specifically, in a controlled experiment, a variable would be any factor that could vary between the two groups. In addition to the two groups, any good scientific study should have three general kinds of variables that are manipulated or controlled: independent variable, dependent variable, and the control or standard variables. The independent variable is the one factor that the scientist changes between the two groups. Specifically, the independent variable is being tested for causation. In fact, it can be thought of as the hypothesis. From the previous example of the drug study, the independent variable is the blood pressure medication. 7. What would be the independent variable from the earlier example of the bacteria? If you were the lead scientist in the above drug study, how would the effectiveness of the drug be determined? In other words, how can a researcher assess whether or not their stated hypothesis was correct? At this point, the dependent variable would be analyzed. This particular variable is going to change in response to the independent variable and determine the conclusion. In the drug study, differences in blood pressure between the two groups are dependent upon the medication How can one be confident that any difference in blood pressures between the two is due to the drug? 8. Eme Thmuelos hur owich me word evol CHAPTER 1 9. What would be the dependent variable from the earlier example of the bacteria? All other factors that need to be kept identical between the two groups are collectively termed the control/standard variables. From the example of the bacteria, control variables would include: strain of bacteria, growth media, culture plate material, moisture, and temperature. 10. Identify five control/standard variables from the blood pressure medication study Experiments can generate two types of data: quantitative and qualitative results. For example. quantitative data are results with assigned values like temperature. In contrast, qualitative data are descriptive results like color. 11. Using the table below, provide examples of each kind of data using the bacteria experiment as your guide. Table 1.1 Types of Scientific Data Qualitative Data Quantitative Data