The manager of a warehouse would like to know how many errors are made when a product’s serial number is read by a bar-code reader. Six samples are collected of the number of scanning errors: 36, 14, 21, 39, 11, and 2 errors, per 1,000 scans each. Just to be sure, the manager has six more samples taken:

33, 45, 34, 17, 1, and 29 errors, per 1,000 scans each

How do the mean and standard deviation change, based on all 12 samples?