Examples of Symmetric Distributions

Oct 13, 2025 by wbrum.org 145 views

In probability theory, a distribution type is a way to describe the behavior of a random variable. There are several types of probability distributions, each with its own characteristics and properties. In this article, we will explore the different types of probability distributions and determine which one has a mean, median, and mode that are all constant.

What are Symmetric, Positively Skewed, and Negatively Skewed Distributions?

A symmetric distribution is a type of probability distribution where the left and right sides of the distribution are mirror images of each other. This means that the mean, median, and mode are all located at the center of the distribution.

A positively skewed distribution, on the other hand, is a type of probability distribution where the right side of the distribution is longer than the left side. This means that the mean is greater than the median, which is greater than the mode.

A negatively skewed distribution is a type of probability distribution where the left side of the distribution is longer than the right side. This means that the mean is less than the median, which is less than the mode.

Which Distribution Type Has a Mean, Median, and Mode that are All Constant?

The answer to this question is a symmetric distribution. A symmetric distribution has a mean, median, and mode that are all located at the center of the distribution, making them all constant.

Why is a Symmetric Distribution the Only One with Constant Mean, Median, and Mode?

A symmetric distribution is the only one with constant mean, median, and mode because of its unique properties. Since the left and right sides of a symmetric distribution are mirror images of each other, the mean, median, and mode are all located at the center of the distribution.

In a positively skewed distribution, the mean is greater than the median, which is greater than the mode. This is because the right side of the distribution is longer than the left side, causing the mean to be pulled to the right.

In a negatively skewed distribution, the mean is less than the median, which is less than the mode. This is because the left side of the distribution is longer than the right side, causing the mean to be pulled to the left.

Examples of Symmetric Distributions

Some examples of symmetric distributions include:

Normal Distribution: The normal distribution, also known as the Gaussian distribution, is a symmetric distribution that is commonly used to model real-valued random variables.
Uniform Distribution: The uniform distribution is a symmetric distribution that is commonly used to model random variables that have a constant probability of occurring.
Bernoulli Distribution: The Bernoulli distribution is a symmetric distribution that is commonly used to model random variables that have two possible outcomes.

Conclusion

In conclusion, a symmetric distribution is the only type of probability distribution that has a mean, median, and mode that are all constant. This is because of its unique properties, which cause the mean, median, and mode to be located at the center of the distribution.

References

Kendall, M. G., & Stuart, A. (1977). The Advanced Theory of Statistics . London: Griffin.
Johnson, N. L., & Kotz, S. (1970). Distributions in Statistics: Continuous Univariate Distributions . New York: Wiley.
Hogg, R. V., & Tanis, E. A. (2001). Probability and Statistical Inference . New York: Prentice Hall.

Frequently Asked Questions

Q: What is a symmetric distribution? A: A symmetric distribution is a type of probability distribution where the left and right sides of the distribution are mirror images of each other.
Q: What is a positively skewed distribution? A: A positively skewed distribution is a type of probability distribution where the right side of the distribution is longer than the left side.
Q: What is a negatively skewed distribution? A: A negatively skewed distribution is a type of probability distribution where the left side of the distribution is longer than the right side.

Glossary

Mean: The average value of a random variable.
Median: The middle value of a random variable.
Mode: The most frequently occurring value of a random variable.
Symmetric Distribution: A type of probability distribution where the left and right sides of the distribution are mirror images of each other.
Positively Skewed Distribution: A type of probability distribution where the right side of the distribution is longer than the left side.
Negatively Skewed Distribution: A type of probability distribution where the left side of the distribution is longer than the right side.
Frequently Asked Questions: Probability Distribution Types =============================================================

In our previous article, we discussed the different types of probability distributions and determined which one has a mean, median, and mode that are all constant. In this article, we will answer some frequently asked questions about probability distribution types.

Q: What is the difference between a symmetric distribution and a skewed distribution?

A: A symmetric distribution is a type of probability distribution where the left and right sides of the distribution are mirror images of each other. A skewed distribution, on the other hand, is a type of probability distribution where the left and right sides of the distribution are not mirror images of each other.

Q: What is a positively skewed distribution?

A: A positively skewed distribution is a type of probability distribution where the right side of the distribution is longer than the left side. This means that the mean is greater than the median, which is greater than the mode.

Q: What is a negatively skewed distribution?

A: A negatively skewed distribution is a type of probability distribution where the left side of the distribution is longer than the right side. This means that the mean is less than the median, which is less than the mode.

Q: What is the normal distribution?

A: The normal distribution, also known as the Gaussian distribution, is a symmetric distribution that is commonly used to model real-valued random variables. It is characterized by a bell-shaped curve and is often used in statistics and data analysis.

Q: What is the uniform distribution?

A: The uniform distribution is a symmetric distribution that is commonly used to model random variables that have a constant probability of occurring. It is characterized by a flat curve and is often used in statistics and data analysis.

Q: What is the Bernoulli distribution?

A: The Bernoulli distribution is a symmetric distribution that is commonly used to model random variables that have two possible outcomes. It is characterized by a binary curve and is often used in statistics and data analysis.

Q: What is the difference between a discrete distribution and a continuous distribution?

A: A discrete distribution is a type of probability distribution where the random variable can only take on a specific set of values. A continuous distribution, on the other hand, is a type of probability distribution where the random variable can take on any value within a given range.

Q: What is the Poisson distribution?

A: The Poisson distribution is a discrete distribution that is commonly used to model the number of events that occur within a fixed interval of time or space. It is characterized by a curve that is similar to the normal distribution, but with a more pronounced peak.

Q: What is the binomial distribution?

A: The binomial distribution is a discrete distribution that is commonly used to model the number of successes in a fixed number of independent trials. It is characterized by a curve that is similar to the normal distribution, but with a more pronounced peak.

Q: What is the exponential distribution?

A: The exponential distribution is a continuous distribution that is commonly used to model the time between events in a Poisson process. It is characterized by a curve that is similar to the normal distribution, but with a more pronounced tail.

Q: What is the gamma distribution?

A: The gamma distribution is a continuous distribution that is commonly used to model the sum of independent exponential random variables. It is characterized by a curve that is similar to the normal distribution, but with a more pronounced tail.

Conclusion

In conclusion, probability distribution types are an important concept in statistics and data analysis. Understanding the different types of distributions and their characteristics is essential for making informed decisions and drawing meaningful conclusions from data.

References

Kendall, M. G., & Stuart, A. (1977). The Advanced Theory of Statistics . London: Griffin.
Johnson, N. L., & Kotz, S. (1970). Distributions in Statistics: Continuous Univariate Distributions . New York: Wiley.
Hogg, R. V., & Tanis, E. A. (2001). Probability and Statistical Inference . New York: Prentice Hall.

Glossary

Mean: The average value of a random variable.
Median: The middle value of a random variable.
Mode: The most frequently occurring value of a random variable.
Symmetric Distribution: A type of probability distribution where the left and right sides of the distribution are mirror images of each other.
Positively Skewed Distribution: A type of probability distribution where the right side of the distribution is longer than the left side.
Negatively Skewed Distribution: A type of probability distribution where the left side of the distribution is longer than the right side.
Discrete Distribution: A type of probability distribution where the random variable can only take on a specific set of values.
Continuous Distribution: A type of probability distribution where the random variable can take on any value within a given range.