Hello,

since I got excellent help with solving my last problem, I thought I would return with another question:

I performed a screen with a series of variables (each with many replicates), including a negative control. After normalization to the negative control (I figured out how to do that), I would like to calculate p-values using the “independent groups t-test” node between the negative control and each variable and eventually visualize the results in a volcano plot.

I have a table that looks something like this:

variable / value

A / 0.8

A / 0.7

B / 2.1

B / 2.0

B / 2.8

C / 0.3

C / 0.2

C / 0.4

negative control / 1.0

negative control / 1.1

negative control / 0.9

and I would like to transform it into a table like that:

variable / p-value (between variable and negative control)

A / 0.1

B / 0.001

C / 0.001

In the configuration of the “independent groups t-test” node, I can only select two groups so I tried to loop over the individual variables using a grouped loop (as suggested in this thread: Paired t-test). Here, I failed to select the correct “group one” and “group two”, since these always change while the loop is executed.

Do you have any suggestions?