Multiple choice

If the aritlunetic mean of $9$ observations is $100$ and that of $6$ observations is $80$, then the combined mean of all the $15$ observations will be

  1. $100$
  2. $80$
  3. $90$
  4. $92$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Combined mean = (Sum of all observations) / (Total number of observations). Sum 1 = 9 * 100 = 900. Sum 2 = 6 * 80 = 480. Total sum = 1380. Total count = 15. Mean = 1380 / 15 = 92.

AI explanation

The combined mean is calculated as (n1 * mean1 + n2 * mean2) / (n1 + n2). The total sum of the 9 observations is 9 * 100 equals 900, and the sum of the 6 observations is 6 * 80 equals 480. Adding these sums gives 1380, and dividing by the total 15 observations yields 1380 / 15, which results in a combined mean of 92.

Keep practicing — related questions