| List I | List II |
|---|---|
| A. Heart | III. Atrial natriuretic factor |
| B. Kidney | I. Erythropoietin |
| C. Gastrointestinal Tract | IV. Secretnin |
| D. Adrenal Cortex | II. Aldosterone |


Find the variance of the following frequency distribution:
| Class Interval | ||||
| 0--4 | 4--8 | 8--12 | 12--16 | |
| Frequency | 1 | 2 | 2 | 1 |