A confounding variable is an extraneous variable that is related to your independent variable and might affect your dependent variable. In an ideal study, there will be no confounding variables.
For example, student accounts have a limit of $100 limit per day, while non-business accounts usually are limited to $500 withdrawals a day. For business accounts, the bank offers $1000 withdrawals in one day. Chase also offers customers a withdrawal limit of $1000 every 24 hours.
Also, just a bit of advice for the ones that do not have direct deposit and/or can't financially maintain $1500 daily balance per month to avoid Chase's $12 monthly maintenance fee, I would suggest you find a local bank or credit union that typically has a free checking account with no minimum balance.