The function expects a matrix x generated from deal_cards_to_rc_grid() where
the first row contains mean values and the second row contains standard deviation
values. It then generates sample_size number of normal random values for each
group, using the respective mean and standard deviation. The resulting data
frame has two columns: one for the group labels and one for the generated values.
The group labels are factors with levels corresponding to the column numbers
prefixed by 'Col'. The generated values are numeric and simulate the data that
would be collected in the study. The function uses the rnorm function from
the stats package for generating random samples.