Mean – Formula, Definition With Examples

Welcome to another informative and enlightening post from Brighterly, the pioneering online platform dedicated to making mathematics easy, engaging, and enjoyable for children. Today, we delve into a topic that forms the bedrock of data interpretation, not only in math, but in everyday life. We’re talking about the mean, an essential type of average, and one of the three pillars of central tendency alongside median and mode. In the forthcoming sections, we’ll explore the definition of the mean, its different types and properties, the formulae used to calculate it, and several practical examples to help consolidate understanding. We’re confident that by the end of this journey, you’ll have a robust understanding of the mean, and most importantly, be confident and excited to apply this knowledge in your daily life and academics.

What Is the Mean?

The mean is a type of average, often utilized to summarize a set of numbers. In everyday language, we often use the term “average” interchangeably with “mean,” but in statistics, it holds a precise definition. When we talk about the mean of a dataset, we’re referring to the sum of all the values in that dataset, divided by the number of values. It provides a centralized value that can often represent a “typical” result within a dataset. For instance, if we have a set of numbers {4, 7, 9, 2, 6}, the mean would be the sum of these numbers (28) divided by the total count of numbers (5), which gives us a mean value of 5.6.

Definition of the Mean in Statistics

In the field of statistics, the mean has a slightly more nuanced definition, often referred to as the expected value. The statistical mean calculates the sum of all the values, each multiplied by their corresponding probability of occurrence, and this sum is then divided by the total number of values. This form of mean is especially useful when dealing with probability distributions, helping us understand what value we’d expect to get on average.

Definition of the Arithmetic Mean

In contrast to the statistical mean, the arithmetic mean is a simpler concept and is the one we most commonly encounter in daily life. It’s calculated by adding up all the values in a dataset and dividing by the number of values. If we consider a group of students’ test scores, the arithmetic mean would give us the average score. It’s a great tool to use when trying to understand a ‘typical’ data point within a dataset.

Properties of the Mean

The mean holds certain properties that make it a valuable tool in both mathematics and statistics. One of the key properties of the mean is that it uses every value in the dataset, making it sensitive to outliers or extreme values. It is also additive, which means that the mean of combined datasets is equal to the sum of their individual means.

Properties of the Mean in Statistics

In statistics, the mean holds a unique property known as the law of large numbers. This law states that as the number of observations increases, the mean of those observations will get closer and closer to the expected value. In other words, the more data we have, the more accurate our mean becomes in predicting outcomes.

Properties of the Arithmetic Mean

The arithmetic mean, like the statistical mean, has its unique properties. It maintains the balancing property, indicating that the sum of the deviations of each data point from the mean is always zero. Also, the arithmetic mean is the only measure of central tendency where the sum of the absolute differences between it and each item in the dataset is minimal.

Difference Between Mean in Statistics and Arithmetic Mean

Though the mean in statistics and the arithmetic mean may seem similar, their use cases and calculation methods differ. The statistical mean is used more in probability and data distributions, accounting for the likelihood of each data point. In contrast, the arithmetic mean treats each data point equally, often used for simpler, real-world calculations like calculating average grades, incomes, or ages.

Formula for Calculating the Mean

The formula for calculating the mean is straightforward and varies slightly depending on whether we’re considering the statistical or arithmetic mean. Generally, it involves adding all data points and dividing by the number of data points.

Writing the Formula for Mean in Statistics

In statistics, the formula for calculating the mean, especially for a probability distribution, is given by: Σ [xi * P(xi)], where xi represents each value in the dataset, and P(xi) is the probability of each value occurring.

Writing the Formula for Arithmetic Mean

When it comes to the arithmetic mean, the formula is even more straightforward: Σxi/N, where Σxi is the sum of all values in the dataset, and N is the total number of values.

Practice Problems on Calculating the Mean

To truly understand the concept of the mean and its calculation, practice is key. Therefore, we encourage our young learners to attempt multiple problems and use the formulas we have discussed. Consider a set of numbers, say {3, 8, 12, 20}, and try to calculate both the statistical and arithmetic mean.


Wrapping up, our exploration of the mean in this post takes us through a fascinating journey of mathematics and statistics. We’ve learned about different types of mean, the properties that define it, and the formulae for calculating it. As with any concept in mathematics, understanding the mean requires practice. We encourage you to apply what you’ve learned here, solve problems, and use mean in practical, real-world scenarios. The quest for knowledge is never-ending, and we are thrilled to be a part of your journey.

Here at Brighterly, we continue our mission to illuminate the path of learning mathematics with clarity, creativity, and comprehensive knowledge. The language of numbers is universal, and understanding it unlocks a world of potential. We’re here to simplify and make math exciting, paving the way for our young learners to become future scientists, engineers, economists, or mathematicians. Join us again as we continue to explore, unravel, and celebrate the magic of mathematics.

Frequently Asked Questions on Mean

Despite being a fundamental concept, the mean often raises several questions among learners. Here at Brighterly, we believe in addressing these inquiries to ensure a deep and thorough understanding. So, let’s explore some frequently asked questions on the mean:

What is the mean used for?

The mean is a measure of central tendency, used to identify the center of a dataset. It helps in understanding the average or typical value in a dataset, making it easier to compare different datasets and draw meaningful conclusions.

How does the mean change with the addition of a new value?

Adding a new value to a dataset will affect the mean. If the new value is above the current mean, the mean will increase, and if the new value is below the current mean, the mean will decrease. The amount of change depends on how far the new value is from the current mean.

Why is the mean considered a reliable measure of central tendency?

The mean is a reliable measure of central tendency because it takes into account every value in the dataset. This comprehensive nature makes it an accurate representation of the data, especially when the data is normally distributed or doesn’t contain extreme outliers.

What is the difference between the mean and median?

While both the mean and median are measures of central tendency, they are calculated differently. The mean is the average of all values in a dataset, while the median is the middle value when the data is sorted in ascending or descending order. The mean can be heavily influenced by outliers, while the median is more resistant to outliers.

Information Sources
  1. Wikipedia – Mean
  2. BBC Bitesize – Mean, Median, Mode and Range
  3. Coursera – Understanding and Visualizing Data with Python

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