Download January 2013

3. Click on the drop-down “Transformation Menu” on the right hand side of the screen to
decide the form of data to use at the prediction stage. The available options are:
• No transformation
• N-score transformation (“Use N-scores” in the menu)
• Box-Cox transformation (“Use BoxCox” in the menu)
 This is an important selection in your investigation. As stated earlier, there is no absolute
correct answer to your decision. Instead, one should rather consult the data in each
individual study. You can always repeat your study using a different transformation type
and compare the prediction results in the end, if necessary.
4. If you select the Box-Cox transformation, there may be an issue with 0 values in the
detrended data set in the original-space. The transformation may require calculation of the
logarithm of 0 and this corresponds to -∞. This is numerically unacceptable, so you are
asked to provide a suitably small value to map 0 to in the original-space for transformation
purposes. The approximation is left to your discretion, as discussed in the Introduction part
of the current screen. A default mapping of 0 into the value 0.001 is assumed when the
screen appears. You can adjust this mapping value with the slider on the lower right-hand
side (Fig. III.B.6).
 If you make a choice other than the Box-Cox transformation, then your investigation is
unaffected by the 0 mapping feature, and you can ignore the slider value.
Fig. III.B.6
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