You and your hypothetical lab partner each develop an experimental plan to test this hypothesis. The two experimental plans are presented below. Evaluate each plan for its pros and cons in the experimental design using the bullet points below. Both experimental plans have some good elements and areas that could be improved.
Experiment A) Mature 2 inch sections (sprigs) of Elodea will be used to measure oxygen production under different light conditions. 5 sprigs will be tested. One will be kept in the dark (no light). The others will be exposed to a light filtered with cellophane. One sprigâs light will be filtered through clear cellophane to receive all wavelengths of light, and the other sprigsâ light will be filtered through red, blue, and green cellophane, respectively. The no-light plant will be kept in a dark cabinet, while the other plants will be together on a counter. Each plant sprig will be placed in equal sized upside-down test tubes in 100ml of tap water so that oxygen bubbles produced by the plant will be trapped at the top of the test tube. A ruler will be used to measure the length of the oxygen pocket collected at the top of the test tube. The experiment will continue until one sprig produces 5 cm of oxygen in the tube.
Experiment B) 3 cm sections (sprigs) of Elodea of various ages will be used to measure oxygen production under different light conditions. 15 sprigs will be divided into 3 groups of 5 sprigs each. One group will receive natural sunlight, one group will be exposed to a blue light bulb under a box to block natural light, and the final group will be exposed to a red light bulb under a similar box to block natural light. Each group of plant sprigs will be trapped under a clear plastic funnel that is covered by an upside-down test tube to collect oxygen bubbles produced by all the sprigs in the group. All groups will be in 100ml of water of the same temperature and pH. The experiment will continue for 24 hours, and then the volume of oxygen gas produced will be measured by multiplying the length of the oxygen pocket by the circle described by the test tube, ?r2. The average volume produced by all groups will be graphed and compared to determine which condition produced the most total volume of oxygen.
Consider the following questions to evaluate experimental plans A and B (DO NOT ANSWER THESE QESTIONS)
What is the independent variable suggested by the hypothesis? Do both plans test the independent variable equally well?
What is the dependent variable in each experiment? Which experimentâs dependent variable best matches the prediction in the hypothesis?
What are the experimental and control groups for each experiment? Which experiment gives the best opportunity to assess the effect of the independent variable?
How does each experiment account for standardized variables? Which experiment do you think is the better controlled experiment?
How is sample size addressed in each experiment? Which would you find to be more convincing?
Does either experiment describe any statistical analyses to be performed on the data?
ANSWER THIS QUESTION: BELOW
Considering your analysis of each of the questions above,write an improved experimental design to test the hypothesis âIf blue light is more effective at promoting photosynthesis, then more oxygen gas (O2) will be produced when plants are exposed to blue-filtered light compared to other wavelengths.âYou may use elements of the above experiments
