Statisticshard · Past Paper
If the arithmetic mean of 10 items is 20 and the mean of 20 items is 10, what is the combined mean of all 30 items?
A13.33
B15
C16.66
D20
✓ Correct Answer: A — 13.33
Combined Mean = (n1*m1 + n2*m2) / (n1+n2) = (10*20 + 20*10) / (10+20) = 400 / 30 = 13.33.
Share this question
More from Statistics
- The median of first seven whole numbers is:
- Two dice are thrown. What is the probability that the sum is less than 4?
- A box contains 10 light bulbs, 3 of which are defective. What is the probability of picking a good bulb?
- If the mean of 4, 7, x, 9 is 7, find the value of x.
- The following is a list of shoe sizes: 5, 6, 7, 7, 8, 9. If a shoe size of 7 is added, which measure will definitely change?