There are three children aged three, four, and five in a room. If another four-year-old child enters the room, what will happen to the mean and variance?

'Mean' may be defined as the average of all the give terms and then add the sum total by the number of terms. It is used to determine the central tendency of the given data in the question.

'Variance' is the measure of how far any set of data are spread out. It is determined by taking the average of all the squared differences from each term to the mean.

In the context, when another four year old child enters the room having a three year, four year and a five year child, the mean age of the children does not change and will remain the same. However the variance will decrease.