I have an anonymized database of a fictional bank with approximately 30,000 entries. These database contains for each customer whether he uses online banking (0 = he doesn't, 1 = he does) and the realised profit (in Euros) of the last year.
So I consider this database as a "sample", since the popularity of the bank's customers is higher. Now I calculated the mean of profits of all customers using online banking and the mean of profits of all customers NOT using online banking.
Now I'd like to test whether these two means differ significantly. Which is the right test to go with? I thought of the t-test, but I'm not sure, that these two means can be considered as based on two samples?