2019 · Q1
Directions: Read the following frequency distribution for two series of observations and answer the two items that follow:
| Class interval | Series-I | Series-II |
|---|---|---|
| 10–20 | 20 | 4 |
| 20–30 | 15 | 8 |
| 30–40 | 10 | 4 |
| 40–50 | X | 2X |
| 50–60 | Y | Y |
| Total | 100 | 100 |
What is the mean of frequency distribution of Series-I?
Elementary MathematicsStatistics
- A33.6
- B35.6
- C37.6
- D39.6
Explanation
Totals give X and Y. Series-I: 20+15+10+X+Y = 100 so X+Y = 55. Series-II: 4+8+4+2X+Y = 100 so 2X+Y = 84. Subtracting gives X = 29, Y = 26. Using class midpoints 15, 25, 35, 45, 55, mean = (20x15 + 15x25 + 10x35 + 29x45 + 26x55)/100 = 3760/100 = 37.6.