Grade 11 → Probability and Statistics → Statistics ↓
Measures of Central Tendency
Measures of central tendency are statistical tools used to measure the central or typical behavior of a data set. These measures provide a way to summarize a large data set with a single, central value, which represents the entire distribution. The three most common measures of central tendency are the mean, median, and mode. Each of these measures provides a different type of information about a data set, and their utility varies depending on the nature of the data.
Meaning
The mean, often referred to as the average, is the sum of all data points divided by the number of data points. It provides a measure of the center of the data by balancing the deviations from this central value. The formula to calculate the mean is:
Mean (μ) = (ΣX) / N
Where:
ΣX
is the sum of all data valuesN
is the number of data values
Example
Consider a set of exam scores: 70, 85, 78, 92, 88.
Mean = (70 + 85 + 78 + 92 + 88) / 5 = 413 / 5 = 82.6
Visual example
Here, the scores are shown as lines and the mean is marked by a red circle at 82.6 on the number line.
Median
The median is the middle value in a data set when it is arranged in ascending or descending order. When the number of observations (N) is odd, it is the middle value. If N
is even, the median is the average of the two middle numbers. When N
is odd, the formula for the median is:
Median = X(N+1)/2
For even number of observations:
Median = (X(N/2) + X(N/2 + 1)) / 2
Example
Consider the following age list: 22, 27, 25, 24, 23.
First, arrange them in order: 22, 23, 24, 25, 27. Middle value or Median = 24
.
Suppose the list is extended to 22, 27, 25, 24, 23, 30.
In sequence: 22, 23, 24, 25, 27, 30.
Median = (24 + 25) / 2 = 24.5
Visual example
For the initial odd-member list, the third point symbolized the median.
Mode
The mode is the value that occurs most often in a data set. If a number does not repeat, the data set has no mode. A set may have one mode (unimodal), two modes (bimodal), or more than two modes (multimodal).
Example
Consider the data set: 2, 4, 4, 6, 8.
Its mode is 4, because it occurs twice as often as any other number.
Visual example
Features of central tendency measures
Mean
- Sensitive to extreme values or exceptions.
- Best for symmetric distributions without outliers.
- Often this represents the 'balance point' of the data set.
Median
- Robust to outliers.
- Useful for skewed distributions.
- Central reason only when the data are ordinal.
Mode
- Can be used with categorical data.
- Indicating the most common value in the dataset.
- Insensitive to external elements.
Which solution should be adopted?
Choosing the right measure of central tendency depends largely on the nature of the data set and the research question. Here are some general guidelines:
- Use the mean for data that is symmetrically distributed with no outliers, as it considers all data points.
- If the data is skewed or has outliers then choose the median for better central value representation.
- Consider the mode when identifying the most common range or score in a distribution.
Conclusion
Measures of central tendency are fundamental concepts in statistics that help describe a data set as a whole and allow comparisons to be made between different data sets. By understanding the mean, median, and mode, one can effectively analyze data and communicate findings in a meaningful way. Whether you are dealing with large data sets in business analysis or smaller sets in academic research, it is important to understand these concepts. As always, the right choice of measure depends on the context and the specific nature of the data involved.