Checking for omitted variable bias

In many organizations, employees at higher job levels in the organization are more likely to be considered high performers. That is, the distribution of performance ratings is not always the same at different job levels.

First, check the difference in job level distribution by gender to see if there is any potential for job level being an omitted variable we need to consider. Then plot the high performer distribution by both gender and job level. Does it look like the gender difference disappears?