PART 2 INTERVAL-SCALE DATA

By conducting a Rasch analysis of basic test (or survey) data, researchers can quickly convert possibly non-equal interval raw data to interval data. To best understand this issue, consider the following Sarah completes a test and earns 95/100, while Pam emis 90/100. The difference between Sarah and Pam may not necessarily be the same as the difference between Tom who earns 50/100 and Henry who scores 55/100. Although the differences (5 points in each case) between the raw scores are the same, the raw score at different parts of the scale may not have die same substantive meaning. Rasch analysis software can be easily used to convert the possibly non-interval raw score data of tests and surveys to an interval scale, and it is that data which is used for statistical analyses. 

Fig. 8. The rapid-scanning spectroscopic time courses for the reaction of 0.17 mM Co(II)-T6 with 100 mM phenol at pH 8.0 in the absence (A, C) and presence (B, D) of 100 mM chloride ion are shown. (A) Reaction in the absence of chloride ion. The time interval between scans is 8.54 ms for the first five spectra, followed by spectra at successively longer intervals afterward (see insets in C and D). The total acquisition time was 1.71 s for the 25 spectra collected only spectra numbers 1-5,7,10,12,15,18,21, and 25 are shown. (B) Reaction in the presence of 100 mM chloride ion. The timing sequence of the spectra is the same as that used in (A). For clarity, spectra 6, 8,10,12,14-16, 18-20, and 22-24 have been omitted. (C) The scaled, subtracted spectra, calculated from the second to the sixth spectrum of part A, correspond to the time-course for intermediate formation. The time course plotted in the inset shows the absorbance change at 560 nm for the complete set of scaled, subtracted spectra as a function of time. (D) Scaled, subtraction spectra numbers 2 to 6, as in part C, for the data part B, with chloride ion present. The inset plot also shows the time course at 560 nm obtained from the complete set. (Taken from Gross and Dunn (55) with permission.]...

The scattering intensity in absolute scale obtained after the standard data normalization procedure contains about 10% of uncertainty in calibration using 1 mm water. This may cause an unnecessary uncertainty in the determination of parameters, a, b, and c. This uncertainty factor, however, can be eliminated by normalizing the scattering intensity by the invariant calculated according to Eq. (2). In the calculation of the invariant, the interval of integration was divided into three parts, 0 < Q < Qmim Qmin[Pg.29]

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