**Question:** The arithmetical average of a number of observations is called

A. Mean
B. Mode
C. Median
D. Range

**Correct Answer:** A. Mean

**Core Concept:**
Arithmetic mean, also known as the mean, is a fundamental measure of central tendency in statistics. It represents the sum of all the observations divided by the total number of observations. In a data set, the mean is calculated by summing all values and then dividing by the total count of values.

**Why the Correct Answer is Right:**
The correct answer is A. Mean because it represents the central value or typical value of a set of observations. It is determined by adding all the values and then dividing by the total count. The mean is important for understanding the overall trend of a data set.

**Why Each Wrong Option is Incorrect:**

B. Mode: The mode refers to the most common value in a data set, which is not the same as the mean. The mode is useful when there is a high degree of skewness in the data.

C. Median: The median is the middle value in a data set when the values are arranged in ascending or descending order. It is useful when the data set has an extreme value or values that are not normally distributed. However, the mean is more general and applicable to all data sets.

D. Range: The range is the difference between the highest and lowest values in a data set. It provides information about the spread or variability of the data but does not represent the typical value of the data set.

**Clinical Pearl:**
Understanding statistical measures like mean, mode, median, and range is essential in interpreting medical data and making clinical decisions. The mean provides a general representation of the data set and is widely applicable.