Merge pull request #2 from Francis-88-cell/patch-1

Update 03c_stats_fitting.Rmd

Author: Francis-88-cell

contents/03c_stats_fitting.Rmd

@@ -78,7 +78,7 @@ where $\widehat{se}(\hat{\theta})$ is the standard error of $\hat\theta$.
 
 Adequate curve fitting requires a sufficient number of evaluated dose points to minimise the error. A minimum of 7 doses should be evaluated, 5 of them at doses equal or lower than 1 Gy, including the 0 Gy dose. Usually, for low-LET radiation (X-rays and $\gamma$-rays) the dose range evaluated is 0--5 Gy, indeed, beyond this dose there is evidence of saturation of the aberration yield which will lead to a distortion of the $\beta$ coefficient in equation \@ref(eq:dose-response-lq) [@ISO19238:2014; @Lloyd1983]. For high-LET radiation, a range of 0--2 Gy is suggested [@IAEA2011].
 
-At higher doses, scoring should aim to detect 100 dicentrics at each dose. However, at lower doses this is difficult to achieve and instead several thousand cells per point should be scored; a number between \num{3000} and \num{5000} is suggested. In all cases, the actual number of cells scored should be dependent on the number of dose points in the low dose region, with the focus on minimising the error on the fitted curve [@Higueras2020].
+At higher doses, scoring should aim to detect 100 dicentrics at each dose. However, at lower doses this is difficult to achieve and instead several thousand cells per point should be scored; a number between 3000 and 5000 is suggested. In all cases, the actual number of cells scored should be dependent on the number of dose points in the low dose region, with the focus on minimising the error on the fitted curve [@Higueras2020].
 
 Opinions vary on how to treat the background level of aberrations in fitting dose-effect data. In general there are three approaches: (a) a dose point at 0 Gy is included in the curve fitting procedure, (b) the zero dose point is ignored, or else (c) the zero dose point is represented in every fitting procedure by a standard background value. Nowadays almost all laboratories include a 0 Gy dose point, and it should always be included for dicentrics, translocations and micronuclei.