Q: Which method can be used to obtain quantified data by comparing three groups within an organization though with a different sample size in each group?
As long as there are no extremities in the groups (outliers) and the groups are normally distributed, there shouldn’t be a problem in analyzing or comparing data for these groups. ANOVA and t-test will work as long as the groups are large enough such that the results will be statistically significant.
Hope that helps. For more information on the various points discussed above, you may refer to the following queries by other researchers: