CS-Cal - Frequently Asked Qestions

Why doesn't the regression lines intersect the y-axis (dose=0) at the measured 0Gy-control measurement?
By definition, the Surviving fraction should be 100% if no treatment was performed with the cells.
So after normalisation, the graph should intersect Y-axis at value 1 where dose=0.
But what if the colony counts for untreated controls where inexact?
Instead of using the experimental - potentially incorrect - control colony numbers, we can estimate the colony number at dose=0 from the regression.
Each single dose implicitely contains the untreated colony number and thus the regression value shold supply a more correct estimate of the dose=0 value, but it might slightly deviate from the measured value (which might be inaccurate).

My graph for photons bends up - Why? The line in the graph represents the best fit of the linear-quadratic model to your data. If the "line" has an unexpected shape, this is due to a problem within your entered data. Most probably: the number of counted colonies might be inaccurate numbers of seeded cells for the different doses was mixed up doses for the different experiments are mixed up empty or non numeric values for colony counts

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