Affect of Slit Width, Scan Rate, and Response Time

The data set available here provides spectra for a solution of benzene in methanol recorded from 230-290 nm using a Perkin-Elmer Lambda 4B spectrophotometer at different combinations of slit width, scan rate, and response time. The original spectra were collected in the late 1980s and print copies archived. To create this data set, the spectra were digitized using the WebPlotDigitizer app available here.

The data set is available as an Excel file with separate tabs for spectra (wavelength, absorbance) showing the affect on the spectrum of a change in slit width, scan rate, and response time. Representative plots of the data are shown below.

File: BenzeneSpectra
Tab 1: SlitWidth
slit widths: 0.25, 1.0, 2.0, and 4.0 nm
scan rate: 20 nm/min
response: 1
Tab 2: ScanRate
slit width: 1.0 nm
scan rates: 5, 10, 20, 60, 120, 200, 300, 750, and 1500 nm/min
response: 3
Tab 3: Response
slit width: 1.0 nm
scan rate: 60 nm/min
response: 1, 2, 3, 4, 5, 6, 7

The response settings likely are as follows (from Lambda 2 spectrophotometer):
1 = 0.1 s; 2 = 0.2 s; 3 = 0.5 s; 4 = 1.0 s; 5 = 2.0 s; 6 = 5.0 s; 7 = 10.0 s

SpectrumSlitWidth SpectrumScanRate SpectrumResponseTime

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Penny Data Set

The data set available here contains masses for 100 circulating U. S. pennies. All pennies in these data sets were minted between 1962 and 1981, a period during which a penny’s composition was 95% copper and 5% zinc with a reported nominal mass of 3.11 g. Some pennies minted in 1982 and all pennies minted from 1983-present are 99.2% zinc (as the core) and 0.8% copper (as a coating), with a reported nominal mass of 2.5 g. The data set is available as an Excel file.

File: penny

One use of the data is shown in the following histogram and superimposed normal distribution curve assuming that μ and σ2 for the population are equivalent to X and s2 for the sample. The total area of the histogram’s bars and the area under the normal distribution curve are equal.

Figure4.10

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Anscombe Data Set for Linear Regression

The importance of visually examining a regression line relative to the data on which the regression is based is a point that cannot be overemphasized. The Anscombe data set, created by the statistician F. J. Anscombe (American Statistician, February 1973, 17-21), provides four sets of data each of which yields the same regression results:

y = 3.00 + 0.500x
correlation coefficient of 0.816

A visual examination of the data sets and their respective regression lines shows that a linear model is inappropriate for all but one of the data sets. The Excel file in this post contains the four data sets, each on a separate tab.

File: Anscombe.xls

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Riboflavin HPLC Data

The data set available here is from the HPLC analysis of of riboflavin in urine. The Excel spreadsheet contains chromatographic data using a fluorescence detector with excitation at a wavelength of 340 nm and detection at a wavelength of 450 nm, and chromatographic data using a UV-Vis detector at a wavelength of 450 nm.

File: RiboflavinHPLC
Tab 1: Fluorescence (time, % fluorescence)
Tab 2: UVVis (time, absorbance)

The following figure provides one presentation of the data that demonstrates the difference between the selectivity of the two detectors. The peak marked with the red asterisk is riboflavin.

Data provided by Jason Schultz, Jonna Berry, Kaelene Lundstrom, and Dwight Stoll, Department of Chemistry, Gustavus Adolphus College.

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