The mean of 10 numbers is 15. If each number is multiplied by 2, what is the new mean?

Explanation

• Multiplying every value by 2 multiplies the mean by 2, so the new mean is 15 × 2 = 30.
• The reason is that the total rises from 150 to 300 while the count stays at 10, and 300 ÷ 10 = 30.
• Adding 2 to every number instead would shift the mean only to 17.
• The count of 10 numbers does not affect the answer, because it appears on both sides of the division.
• The standard deviation would also double, while the variance would become four times as large.