Question

Suppose an airline claims that its flights are consistently on time with an average delay of at most 15 minutes. It claims that the average delay is so consistent that the variance is no more than 150 minutes. Doubting the consistency part of the claim, a disgruntled traveler calculates the delays for his next 25 flights. The average delay for those 25 flights is 22 minutes with a standard deviation of 15 minutes.

How did you know to test the variance instead of the mean?

Short answer

From the claim, it is evident that researchers are tested for variance not for mean that the claim is the variance is no more than $150$minutes.

Step-by-step solution

Given information

Given in the question that

A disgruntled traveler calculates the delays for his next 25 flights. The average delay for those 25 flights is 22 minutes with a standard deviation of 15 minutes.

Solution

The word variance directs to a statistical measurement of the distance between numerals in a data set. More precisely, variance measures how far each number in the set is from the mean and therefore from every additional number in the set. Variance is frequently showed by this symbol: ${\sigma }^2$. It is used by both analysts and vendors to select volatility and market security.

So here the claim will be variance is not more than the $150$

Thus it means that the researchers are tested for variance, not for the mean.