Test set: Difference between revisions
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Reference to Ian Tickle et al. for sigma(Rfree)/Rfree = 1/sqrt(2n) |
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==How precise is the estimate of R<sub>free</sub> for a certain number of test set reflections?== | ==How precise is the estimate of R<sub>free</sub> for a certain number of test set reflections?== | ||
The estimate for the relative error of [[iucr:Free_R_factor|R<sub>free</sub>]] is 1/sqrt( | The estimate for the relative error of [[iucr:Free_R_factor|R<sub>free</sub>]] is 1/sqrt(2n), where n is the size of the test set (Tickle et al., Acta Cryst. (2000) D56 , 442-450). So if n is 1000, and the [[iucr:Free_R_factor|R<sub>free</sub>]] is 31%, you would expect its relative error to be 31%/sqrt(2000), which is about 0.7%. | ||
==How many reflections do you need to get a good estimate of the sigmaA values (as a function of resolution) needed to calibrate the likelihood target?== | ==How many reflections do you need to get a good estimate of the sigmaA values (as a function of resolution) needed to calibrate the likelihood target?== | ||