Question

From a population of 200 elements, the standard deviation is known to be 14. A sample of 49 elements is selected. It is determined that the sample mean is 56. The standard error of the mean is _____. a. 2 b. greater than 2 c. 3 d. less than 2

Answer 1

a. 2

Explanation:

Central Limit Theorem

The Central Limit Theorem establishes that, for a normally distributed random variable X, with mean
`\mu` and standard deviation
`\sigma`, the sampling distribution of the sample means with size n can be approximated to a normal distribution with mean
`\mu` and standard deviation
`s = (\sigma)/(√(n))`.

For a skewed variable, the Central Limit Theorem can also be applied, as long as n is at least 30.

For a proportion p in a sample of size n, the sampling distribution of the sample proportion will be approximately normal with mean
`\mu = p` and standard deviation
`s = \sqrt{(p(1-p))/(n)}`

Standard deviation is known to be 14.

This means that
`\sigma = 14`

Sample of 49

This means that
`n = 49`

The standard error of the mean is

`s = (\sigma)/(√(n)) = (14)/(√(49)) = (14)/(7) = 2`

So the correct answer is given by option a.