Proportionality Test - Assignment Example

Practical report: Assessment questions Practical report: Assessment questions Comment on the groups choice of volume and say what conditions you would have used for the time that your group was given*. Explain clearly how you arrived at your answer. With 70 seconds given from the experimental results the time that is nearest to 70 seconds is 66.94 seconds that responds to 123 μL is within the boundaries of 70 seconds. However, the group should have settled on 22 μL which responds to 15.37 seconds (Campell & Reel 2008, Pg 32). For the time that the group was given the first action would have been to determine the value for the titre. For example, if 30 drops of starch to 3 ml of ascorbic acid is at the end point then it is said the titre is 30 drops and then the time is noted for the reaction to be completed. Assuming it is four seconds (Nester et al. 2011, Pg. 65). Then using proportionality we can approximate the volume required for the ascorbic acid to react in 70 seconds. Assuming the amount of starch added is constant as follows. Volume of ascorbic acid Drops of starch Time (seconds) 3 ml 30 4 ? 30 70 Volume of ascorbic acid = Therefore, the volume of ascorbic acid will be 52.5 ml, and the reaction time will be 70 seconds (Leboffe 2012, Pg. 12). 2) Say how you would have improved upon this groups design referring to experimental principles: hypothesis, treatment, control, observation, interpretation. Consider the target time assigned to your group* for the practical lab in planning your answer. All experiments involve three things: randomization, replication and control charts. Randomization: Assigning the factors to be tested during the test is what is called randomization. Through randomization, systematic errors are removed in an operation. This is because every unit will have an equal chance of receiving equal treatment. In connection to this factors should be chosen randomly (Emil et al. 2012, Pg. 343). Replication: It involves carrying out an experiment using the same conditions. However, in experimental designs it means the number of distinct units under the experiment. Through repetition, it will be possible to estimate the error variance. For example, in order to calculate the error variance for the above experiment, x (µ= 124.2 μL) 22 10444 39 7259 88 1310 99 635 111 174 123 2 136 144 150 666 350 51076 Total ∑ 71710 Standard deviation = √ Standard error = SD/√n= 33.47 Local control: It means controlling all the other factors apart from the ones which are being investigated. This enables the control of all the other factors which may interfere with the experiment. Completely Randomized Design (CRD) CRD is a system where each experimental unit is completely assigned at random so that each unit has an equal chance of being chosen. Analysis of variance Treatment groups n µ S2 Vol. of ascorbic acid 9 124.2 (1) 8962.4 Time (seconds) 9 76.48(2) 1713.96 Hypothesis Ho: The mean time required to complete the reactions does not differ (µ1=µ2) H1: The mean times required to complete the reactions varies (µ1 ≠µ2) Assumptions The samples were withdrawn randomly and independently from the population and that they are regularly distributed. Anova: Single Factor SUMMARY Groups Count Sum Average Variance Column 1 9 1118 124.2222 8951.944 Column 2 9 688.3 76.47778 1714.476 ANOVA Source of Variation SS df MS F P-value F crit Between Groups 10257.89 1 10257.89 1.923399 0.184502 4.493998 Within Groups 85331.36 16 5333.21 Total 95589.26 17         From the table, it is clear that Fcal < Fcrit. Therefore, the mean times required to complete the reaction differs significantly. 3) Write a methods section for the procedure you propose in correct scientific English and style as if it were being reported in a scientific paper after the conclusion of the experiments Chemicals and reagents Ascorbic acid, distilled water, 5% starch (indicator), O.5gm of ascorbic acid is measured and mixed with 500ml of water. 25ml of equal portions is poured into four clean containers. 5ml of 5% starch is then added to each of the containers. The burette is then filled with iodine solution and the initial volume is recorded. The iodine solution is then added slowly to the ascorbic acid. It will be noted that blue, black solution of the iodine solution disappears with each addition of iodine because iodide ion is formed. The volume of the iodine used is then recorded. The procedure is then repeated for all the four tubes (Grapper & Smith 2013, Pg. 6). References Campbell, N.A. and Reece, J.B. (2008) Biology (8th Ed.). San Francisco, California: Pearson Education. Nester, E., Anderson, D., & Evans, R. (2011) Microbiology: A Human Perspective (7th Ed.) Washington: McGraw-Hill Science. Leboffe, M., Pierce, B. & Ferguson, D. (2012) Microbiology Laboratory Theory & Application (2nd Ed.) New York: Morton Publishing Company. Gropper, S. and Smith, J. (2013). Advanced Nutrition and Human Metabolism. United States of America: Yolanda Cossio. Emil, S. Wayne, W. & Robert, R. 2012. Chemical Principles in the Laboratory.3rd Ed. New York: Wiley. Appendix 1: Table showing the different reaction times and volumes Time (seconds) Vol. of ascorbic acid 15.37 22 36.25 39 59.56 88 58.71 99 84.9 111 66.94 123 106.06 136 108.57 150 151.94 350 Graph showing Volume of ascorbic acid which reacted with Time (seconds) Read More