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Consider the random variable X with mean and standard deviation as​ shown:

Mean SD
X 102 33

a. What is the mean of 3x + 27?

b. What is the standard deviation of 3X ​+ ​27?

1 Answer

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Final answer:

The mean of the transformed variable 3X + 27 is 333, and the standard deviation is 99.

Step-by-step explanation:

When considering a random variable X with a mean of 102 and a standard deviation of 33, and looking to calculate the mean and standard deviation of a transformed variable 3X + 27, we apply some basic rules of statistics:

Mean of 3X + 27

To find the mean of the new random variable, we use the formula:

Mean of aX + b = a × (Mean of X) + b

Thus, the mean of 3X + 27 is 3 × 102 + 27 = 333.

Standard Deviation of 3X + 27

The standard deviation of a linear transformation ax + b is the original standard deviation multiplied by the absolute value of a:

Standard Deviation of aX + b = |a| × (Standard Deviation of X)

Hence, the standard deviation of 3X + 27 is |3| × 33 = 99.

User Douglas Leeder
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