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) | =(C14-F9)/E9 | ||
| Std Deviation | 0.07 | =(F11/E9)* (1 + 1/C17+((C14-C18)^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