I've got some sample data.. what it represents isn't really important. The first group is 782, 965, 948, 1181, 1414, 1633, 1852. The second group is 593, 672, 750, 988, 1226, 1462, 1698. The means of each I calculated to be about 1253 and 1055 respectively.

The question is to find a 95% confidence interval for the different in the means. I'm confused because no standard deviation is given (and usually is in our class), so I'm a bit unclear as how to standardize this to find the CI using the methods I know about. Can anyone help me out?