Make Data like this:
Data={'The calculated means for ERP0 are ','The standard deviations for ERP0 are ', 'The calculated means for ERP08 ', 'The standard deviations for ERP08 are '; mean0 stdev0 mean08 std08}
Notice the ";" instead of ",". The point is to make Data a 2x4 cell array rather than 1x8 array, then the fprintf() code you have should get what you want.