CHEMISTRY 231
Spring, 2013 Homework Set 1
Solutions
Statistics
Calculations
1. Download
the file on the Chem 133 website labeled filterHW.txt. (this gives the time in
minutes and the signal in fluorescence units) and transfer to an Excel File. Print a table from Excel showing two columns
collected over the first 30 s period.
2.
Make a plot of the raw data from above and also data processed with a 2
s moving average over both the first 30 s and over the first 4 min. This can be done by either using Excel's
Plotting routines or by creating a 2 s moving average using a new column in
Excel.
Statistical Problem Solutions – This link
goes to the Excel File.
Here are 4 plots (A, B, C, and D
corresponding to 30 s data with 2 s moving average trend line, 30 s data with 2
s moving average using Excel average function, 4 min data with 2 s moving
average trend line, and 4 min. data with 2 s moving average using Excel average
function, respectively)
3.
Given the following data, determine the concentration of levoglucosan in
an unknown and the standard deviation in its concentration.
Standards  Unknown
Data

Levoglucosan
Area


Levoglucosan
conc

Levoglucosan
Area

Levoglucosan
conc


(ug/mL)

(ug/mL)


0.5  469.11

Unknown

2276.40 
1  826.57


2  1578.66


5  3973.85


10  8043.47

Levoglucosan
conc

Levoglucosan
Area


(ug/mL)


0.5  469.11

LINEST Results  
1  826.57

m  799.7293  19.33312  b 
2  1578.66

Sm  6.067866  30.9699  Sb 
5  3973.85

R^2  0.999827  47.7013  Sy 
10  8043.47


Levoglucosan conc  Levoglucosan Area  
(ug/mL)  
Unknown  2276.40  
equation  
Number Stds  5  =COUNT(B4:B8)  
Mean Area  2978.33  =AVERAGE(C4:C8)  
Sum of (xi  mean x)^2  61.8  =DEVSQ(B4:B8)  
equation  
Conc.  2.82  (ug/mL)  =(C14F9)/E9  
Std Deviation  0.07  =(F11/E9)* (1 + 1/C17+((C14C18)^2/(E9^2*C19)))^0.5 

Uncertainty  0.21  =TINV(0.05,3)*C22  
Uncertainty_2*  0.09  =C23/(C17)^0.5  
*calculated based on HPLC instructions 
updated 2/8/13