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UV/Vis Spectroscopy

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    Classroom Exercise #6: Work-Up of UV-Vis data

    There is an Excel spreadsheet from the platereader that accompanies this exercise.  You will need to use your computer to do the statistics to complete the questions.


    In this exercise, to test their skills to make a solution, each person in a class made a UV-Vis solution of a blue dye.  The TAs and professor also made the same solution.  The UV-Vis absorbance of each solution was collected with a platereader at 630 nm after the students pipetted 300 uL of their solution in a 96 well plate.  Data are shown in the accompanying spreadsheet. 

    The class data is below, with 3 replicates per student (horizontally i.e. A 1&2&3 are the same person, A 4-6 are the same person, B1&2&3 are the same person, etc). The TA/prof data is in a column below the class data.  I give you the average and s.d.

    1. Calculate the mean absorbance value for each person in the class.

      1. What is the mean and standard deviation of the student data? Use the per person data for this calculation.

      2. Whose standard deviation is higher, the students or the TAs?  Why?

      1. What percentage of student values are within 1 standard deviation of the TA/prof value?


        Within 2 standard deviations?


        What percentage were outside 3 standard deviations?


      2. If the data sampled the same normalized distribution, what percentage of values should have been within 1 standard deviation? 


        Within 2 standard deviations?


    1. Assume the TA/prof average value is the true value. Calculate the percent error for each person.

    2. Use the Q-test formula: can you throw out either the highest or the lowest student value? Why do think you can/cannot throw it out?

      1. What are the likely sources of error for those within 1 standard deviations of the TA/prof value?

      2. What are the likely sources of error for those within 2 standard deviations of the TA/prof value?

      3. What are the likely sources of error for those outside 3 standard deviations of the TA/prof value?


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