Question

Given a randomly selected data point, how do we determine if it is unusual (statistically significant)? Begin your answer with a direct answer to the question, then explain your answer in more depth.

Answer 1

For a randomly selected data point, we look at the distance from the mean in terms of standard deviation, to determine whether it is usual or unusual.

All data values which are within the range of 2 standard deviation from mean value, i.e. either within 2 standard deviation below range or above range of mean, are considered as usual data point.

All data values which are outside the range of 2 standard deviation from mean value, i.e. either less than 2 standard deviation below range or more than two standard deviation above range of mean, are considered as unusual data point.

So, for any x value, if it is less than or more than , then it is an unusual data point.