Statisticsmedium · Past Paper
If the mean of 10 observations is 20 and another 10 observations is 30, the combined mean is:
A25
B20
C30
D50
✓ Correct Answer: A — 25
Combined mean = (n1*x1 + n2*x2) / (n1 + n2) = (200 + 300) / 20 = 25.
Share this question
More from Statistics
- For a data set with 50 items, the mean is 100. If each of the first 25 items is increased by 2, and each of the last 25 items is decreased by 2, the new mean is:
- The range of the data 25, 18, 32, 45, 12, 50 is:
- If the sum of observations is 500 and the mean is 25, how many observations are there?
- A bag contains 5 red balls and 3 green balls. What is the probability of drawing a red ball?
- If the mean of 10 observations is 15, and 2 is added to each of first 5 and 4 is added to each of last 5, the new mean is: