| ECG Abnormality | Clinical Condition | 
|---|---|
| A) Enlarged P wave | III) Atrial enlargement | 
| B) Prolonged P-R interval | I) Bradycardia | 
| C) Shortened Q-T interval | IV) Hypercalcemia | 
| D) Elevated S-T segment | II) Myocardial infarction | 
| 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 |