Mean:
The mean is a measure of central tendency that represents the average value of a set of observations. It is calculated by summing up all the observations and dividing the sum by the total number of observations.

Explanation:
The statement "It is representative of the whole group" is true about the mean. Let's understand why:

1. Definition of Mean:
The mean is calculated by summing up all the observations and dividing the sum by the total number of observations. It provides a single value that represents the central tendency of the data set.

2. Balance of Positive and Negative Deviations:
The mean takes into account both positive and negative deviations from the average. It considers the magnitude and direction of each observation, resulting in a balanced representation of the entire data set.

3. Sensitivity to Extreme Values:
The mean is sensitive to extreme values or outliers in the data set. It gives more weight to extreme values, which can significantly impact the overall value of the mean. This sensitivity makes the mean a representative measure of the whole group as it considers all observations, including outliers.

4. Equal Weighting:
Each observation in the data set is given equal weight when calculating the mean. This means that every data point contributes to the overall value of the mean, providing a fair representation of the entire group.

5. Mathematical Accuracy:
Mathematically, the mean is the sum of all observations divided by the total number of observations. This ensures that the mean accurately represents the entire data set by taking into account every observation.

Conclusion:
The mean is a representative measure of the whole group because it considers all observations, both positive and negative deviations, and gives equal weight to each data point. It accurately represents the central tendency of the data set and provides a balanced representation of the entire group.