Continuous, Discrete, and Nominal Variables

  1. Question 1: Provide 2 examples each (other than those mentioned above) of continuous, discrete, and nominal variables.
    1. Continuous (can be measured in fractions and include things like temp and mass)
      1. Weight
      2. Height
    2. Discrete (can only be measured as integers)
      1. Number of students in a class
      2. Number of cookies in a jar
    3. Nominal (observations that can be quantified and are given names)
      1. Genotype
      2. Nationality
    4. Question 2: For the following experiments, identify the dependent (the response to the manipulation; data collected) and independent (variable being manipulated; involving direct cause and effect; location or groups) variables, and explain (which requires some justification on your part) whether the independent variable is a fixed (cause and effect are being examined) variable or a random variable (encompassing a number of possible effects, or effects whose level are not determined by the experimenter).
      1. Seasonal changes (IV) in lipids, diet and body composition of free-ranging black-tailed prairie dogs (DV)
        1. I believe that the independent variable is a random variable because
      2. The effects of impoundment (IV) on the community structure of freshwater mussels in the Neosho River, Kansas (DV).
        1. I believe that the independent variable is a fixed because
      3. Effect of various doses of chlorpromazine (IV) on formation of 3-methoxytyramine and normetanephrine in mouse brain (DV).
        1. I believe that the independent variable is a random because we will have different doses and the effects that they will have cannot be specifically measured because the outcomes may vary.
      4. The effect of vegetation changes (IV) following deforestation on water yield and evapotranspiration (DV).
        1. I believe that the independent variable is a fixed because the change in vegetation directly effects the rate of transpiration and evaporation. The more the vegetation the more likely changes in evapotranspiration will be experience.
      5. Direct proinflammatory effect of C-reactive protein (IV) on expression of adhesion molecules in human endothelial cells (DV).
        1. I believe that the independent variable is a fixed because we would be measuring the cause and effect of something.
      6. Question 3: Which of these two sets of results (the left or the right) would give you more confidence in concluding that the addition of glucose had an effect on the rate of contraction of the contractile vacuole? Justify your answer based upon the amount of variation present in the data.
        1. The results on the right would give you more confidence in concluding that the addition of glucose influenced the rate of contraction of the contractile vacuole. On the left one the results on the bar graph seems to be overlapped, hence we many do not conclude that there is a significant difference between the two. On the right side graph the results does not overlap and there is a difference between the two data sets hence this side would seem to be more confident in concluding that the addition of glucose had an effect on the rate of contraction of the contractile vacuole.
      7. Question 4: Explain how and why you might modify the sample sizes (number of experimental units) used in this experiment if you had prior knowledge (from a preliminary trial – always a good idea) that the distribution on the right was the correct one.
        1. A sample size is modified by going for a sample size which has constraints in resources. There is need to modify the sample size to increase the confidence level in the research. Biasness and missing the correct results is avoided when the sample size is modified. The margin error also reduces when the sample size is modified
      8. Question 5: For each of the following examples, indicate the actual sample size, i.e., number of experimental units, for each treatment (just counting the potential observations will give you the wrong answer!)
        1. The effect of sun exposure on the surface area of privet leaves: the surface area of 20 leaves from each of 3 privet plants are measured in a sun-exposed area, and also in a shaded area.
          1. I believe that its 60.
        2. The effect of fertilizer on the growth rate ofBrassica rapa: 10 pots are planted with 5 plants per pot, and fertilizer is added to 5 of the pots. The growth rates of each plant are measured over the course of 2 weeks.
          1. I believe that its 50.
        3. The effect of the presence of predators on the rate of metamorphosis of tadpoles ofRana catesbeiana: 20 aquaria with 15 bullfrog tadpoles in each are filled either with artificial pond water (10 aquaria) or with artificial pond water taken from aquaria that housed largemouth bass, Micropterus salmoides (10 aquaria), and the amount of time required for the individual tadpoles to develop into frogs is recorded.
          1. I believe that its just 300.
        4. Question 6: Which of the 2 graphs would be the best (i.e., smoothest) presentation of these data, and why?
          1. Chart 2 would be the smoothest. Chart 1 may be more accurate in terms of individual point plotting, but chart 2 presents the data in a way that the trend or curves are easily understood and interpreted.
        5. Question 7: Which of the 2 software packages appears to do a better job of generating random numbers? What is the basis for your conclusion, i.e., what is the expected distribution, and which method comes the closest to meeting this expectation?
          1. The software used for chart 4 did a better job I feel of generating random numbers. The basis for my conclusions is because the chart it generated presents the data more clearly and allows for it be “read” better. I believe the expected distribution to have a sharp drop (which it did) and the method I felt that came closest to meeting this expectation (I think you were asking just for overall) was what we did for Chart 1.

 

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