CHEM 1406                                                                             Measurement Laboratory

(revised 7/01/03)

 

Blood Glucose Measurement:

 

(BE SURE TO DISPOSE OF THE USED TEST STRIP IN THE APPROPRIATE

 MANNER FOR A BILOGICAL HAZZARD!)

 

 

            Meter reading = ____________________

                       

Time of reading, ____________________

Circle one:

 

                                    Fasting        or       Non-fasting

 

                        Normal Fasting   ~ 75 - 110 mg/dL

                       

 

 

Data Analysis, Blood Glucose Monitor

 

 

            Define - accuracy __________________________________________

 

 

            _________________________________________________________

 

 

            _________________________________________________________

 

 

 

            Define - precision  __________________________________________

 

 

            _________________________________________________________

 

 

            _________________________________________________________

 

 

 

 

 

 

 

 

 

 

 

CHEM 1406                             Blood Glucose Measurements                        page 2

 

Data:  Using the "glucose standard solution" provided, take five separate glucose

readings.  Record the five readings in the table below.  (These used test strips pose

 no biological hazard.)

 

                                Table 1:  Observations

Sample #

Observed reading

 

 

 

 

 

 

 

 

 

 

 

           

 

Calculate the mean (average) =  _____________

            Show work:

 

 

 

 

            Complete the following table:

            Table 2, Calculations

Sample #

   Deviation from the mean

[(mean value) - (sample value)]

                value D

  Square of deviation

       from the mean

               D2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CHEM 1406                             Blood Glucose Measurements                        page 3

 

 

  

 

 

from: http://www.chem.vt.edu/chem-ed/data/precision.html

 

Calculate the standard deviation for the observed readings using the

"glucose standard."

 

 

   Standard deviation =  __________________

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Calculation of the Standard Deviation: (for ungrouped data)
The "Standard Deviation" for ungrouped data can be calculated in the following steps:

1.        all the deviations (differences) from the arithmetic mean of the set of numbers are squared;

2.        the arithmetic mean of these squares is then calculated;

3.        the square root of the mean is the standard deviation

Non-mathematical people always find this a bit complicated at first, but don't despair, there is an example to follow that should take the sting out of it.

Example:
Given the set of numbers {20, 23, 25, 26}, the "Standard Deviation" can be calculated as follows:

Step 1:
The arithmetic mean of these numbers is found to be equal to 23.5
[eg. arithmetic mean = (20+23+25+26)/4 = 23.5]. The deviations from the mean are respectively:

1.        23.5 - 20 = 3.5

2.        23.5 - 23 = 0.5

3.        25 - 23.5 = 1.5

4.        26 - 23.5 = 2.5

The squares of these deviations are:

1.        3.5^2 = 12.25

2.        0.5^2 = 0.25

3.        1.5^2 = 2.25

4.        2.5^2 = 6.25

Step 2: The sum of these squares is 12.25 + 0.25 + 2.25 + 6.25 = 21. This is now divided by (n-1), which is 3, to get 7.

NOTE: Some books show division by "n". However, when calculating the Standard Deviation of small sample, a better estimate of the parent group is obtained by dividing by (n-1) instead of dividing by "n". For large "n", the difference between using "n" or "n-1" is small.

Step 3:
Finally, the square root of 7 is approximately 2.6457513

Answer:
In summary, the Standard Deviation of the set of numbers {20, 23, 25, 26} is 2.6457513

 

From, http://www.bjmath.com/bjmath/Stats/sd.htm