1. Calculate the midpoint for each class interval: (Lower limit + Upper limit) / 2.
- For 20-40: (20 + 40) / 2 = 30
- For 40-60: (40 + 60) / 2 = 50
- For 60-80: (60 + 80) / 2 = 70
- For 80-100: (80 + 100) / 2 = 90
- For 100-120: (100 + 120) / 2 = 110
- For 120-140: (120 + 140) / 2 = 130
- For 140-160: (140 + 160) / 2 = 150
- For 160-180: (160 + 180) / 2 = 170
- For 180-200: (180 + 200) / 2 = 190
2. Multiply each midpoint by its corresponding frequency (number of families).
- 30 * 6 = 180
- 50 * 9 = 450
- 70 * 11 = 770
- 90 * 14 = 1260
- 110 * 20 = 2200
- 130 * 15 = 1950
- 150 * 10 = 1500
- 170 * 8 = 1360
- 190 * 7 = 1330
3. Sum all the products from step 2 to get the total sum of (midpoint * frequency).
- Total = 180 + 450 + 770 + 1260 + 2200 + 1950 + 1500 + 1360 + 1330 = 11000
4. Sum all the frequencies to get the total number of families.
- Total families = 6 + 9 + 11 + 14 + 20 + 15 + 10 + 8 + 7 = 100
5. Divide the total sum from step 3 by the total number of families from step 4 to find the mean.
- Mean = 11000 / 100 = 110
The mean daily expense is Rs. 110.
Parent Tip: Review the logic above to help your child master the concept of statistics worksheets.
