[BioC] Definition of the CellHTS2 normalizePlates parameter scale

[c.lieftink at nki.nl]

Hello everyone,

The cellHTS2 method normalizePlates has a parameter called "scale". The two values are "additive" vs. "multiplicative".  Although it seems be some basic statistical knowledge I am not able to find a clear definition of additive versus multiplicative data scale. Can anyone provide me with one? I have searched the internet but could not find one.

2) In cellHTS2 the scale value has the following influence on normalizing with "median":
additive: the measurement is divided by the median
multiplicative: the median is subtracted from the measurement

I assume that a cellcount is additive data. It is my understanding that the most used method for normalization in RNAi screens is dividing by the median. However, cellHTS2 does not offer that option for additive data. Would it a good idea when the end user is offered to possibility to choose for his/her (additive) data to subtract or divide by the median?

3. I am working with cellHTS2 2.2.5. Maybe something has changed in 2.4.1, but I was not able to find any release notes.

Best regards,

Cor