This question is solved using the central limit theorem, giving an answer of:
Fourth option, approximately normal with mean of 140 seconds and standard deviation of 10 seconds.
Central Limit Theorem
The Central Limit Theorem establishes that, for a normally distributed random variable X, with mean
and standard deviation
, the sampling distribution of the sample means with size n can be approximated to a normal distribution with mean
For a skewed variable, the Central Limit Theorem can also be applied, as long as n is at least 30.
Mean of 140, standard deviation of 20, sample of 4:
By the Central Limit Theorem, the distribution is approximately normal.
Mean is the same, of 140.
, thus:
![s = \frac{\sigma}{\sqrt{n}} = \frac{20}{\sqrt{4}} = 10](https://tex.z-dn.net/?f=s%20%3D%20%5Cfrac%7B%5Csigma%7D%7B%5Csqrt%7Bn%7D%7D%20%3D%20%5Cfrac%7B20%7D%7B%5Csqrt%7B4%7D%7D%20%3D%2010)
Thus, the correct answer is:
Fourth option, approximately normal with mean of 140 seconds and standard deviation of 10 seconds.
For another example of the Central Limit Theorem, you can check brainly.com/question/15519207