Try this...
IF {table.rating} < 1.5
THEN "dissatisfied"
ELSE IF {table.rating} > 1.5 and {table.rating} < 2.5
THEN "Not up to expectations"
ELSE IF {table.rating} > 2.5 and {table.rating} < 3.5
THEN "Fair"
You would then use a summary to average all the responses, and use the same formula to apply "dissatisfied", etc. to the summary (total average). Just replace "{table.rating}" with your summary field name.