My textbook sets this question:
In each of the following sentences, a word has been used in sentences in different ways. Choose the option corresponding to the sentence in which the usage of the word is incorrect or inappropriate.
The average of 3, 4, 5, 7. and 10 is 6 whereas the mean is 5.
The books says that it is wrong and median should be used instead:
In this sentence, mean has to be replaced with median for the sentence to make sense.
My question is: isn't mean correct? For years I've studying the word mean in mathematics, and now the book says: use median.
I don't think the sentence is wrong due to the mean being written as "6", because even if I write the wrong mean, the usage of the word is correct, I'm just writing the wrong answer.
If you look at this link, it says, mean should be used for symmetrical data sets, and median for skewed data, In the above sentence, the data being skewed my guess is that is probably the reason median is being used and not that mean is written as 6 whereas actually median is 6.
Mean or Median