Confidence interval when data is in range

#1
I am trying to calculate the confidence interval when data is given in range.

Example:

Rather than telling their exact age in years, 9 sample students from a class tell their age as:

(23 +/-1) ; (22 +/-1) ; (20 +/-2 ) ; (25 +/-2) ; (24 +/-2) ; (25 +/-3) ; (22 +/-3) ; (24 +/-4) ; (25 +/- 4 )

How do we calculate XY% confidence interval in such scenario.