Exploring Gamma Distribution in Statistics
Statistics is one of the most crucial branches of mathematics that can be used to analyze, interpret, and draw conclusions from data. A critical aspect of any statistical study involves analyzing the distribution of data.
One such distribution widely used in statistics is the Gamma Distribution. In this article, we will explore what Gamma Distribution is, its parameters, and how to plot a Gamma Distribution in Python.
Gamma Distribution: What is it?
Gamma Distribution is a continuous probability distribution used to model the time or number of events until a specific number of successes occurs.
It is widely used in actuarial science, economics, engineering, and sciences. Gamma Distribution is used when the distribution of events follows a Poisson process, and the time between Poisson events follows an exponential distribution.
Gamma Distribution has two shape parameters: alpha () and scale parameter: . The gamma distribution can take on many shapes, from a bell curve to positively skewed distributions to a leftskewed shape.
The shape of the Gamma Distribution depends on the values of alpha and beta.
Plotting a Gamma Distribution in Python – Single Gamma Distribution
The easiest way to create a Gamma Distribution is by using Python. Let’s look at how to plot a single Gamma Distribution.
import numpy as np
import matplotlib.pyplot as plt
from scipy.stats import gamma
alpha = 1.5
beta = 2
x = np.arange(0, 20, 0.1)
plt.plot(x, gamma.pdf(x, alpha, scale=beta), label='=1.5, =2')
plt.title('Gamma Distribution  Single Gamma')
plt.xlabel('Xaxis')
plt.ylabel('Yaxis')
plt.legend()
plt.show()
The above code generates the following graph:
The above graph shows how the Gamma Distribution for Shape Parameter =1.5 and Scale Parameter =2 looks like.
The xaxis represents time taken to achieve the given success, while the yaxis represents the probability of achieving that success.
Multiple Gamma Distributions
In some cases, you may need to plot multiple Gamma Distributions in Python. For example, you may want to compare the probability distribution of two different data sets.
In such cases, you can use the following code to create multiple Gamma Distributions.
import numpy as np
import matplotlib.pyplot as plt
from scipy.stats import gamma
define_alpha_beta_range = [(1, 2), (5, 2)]
#define colors for plotting
colors = ['blue', 'green']
#initialize the xaxis range
x = np.arange(0, 10, 0.1)
#loop through the shape and scale parameters and plot the gamma distribution
for idx, (alpha, beta) in enumerate(define_alpha_beta_range):
y = gamma.pdf(x, alpha, scale=beta)
plt.plot(x, y, color=colors[idx], label='={}, ={}'.format(alpha, beta))
plt.title('Gamma Distribution  Multiple Gamma')
plt.xlabel('Xaxis')
plt.ylabel('Yaxis')
plt.legend()
plt.show()
The above code generates the following graph:
The above graph shows how two different Gamma Distributions look when plotted together.
The blue line is for =1, =2 while the green line is for =5, =2.
Common Distributions in Python
Python provides many builtin libraries for commonly used distributions, making it a handy tool for statistical analysis. Some common distributions are:

Normal Distribution: The bell curve, also known as the Gaussian or standard normal distribution, has a mean of zero and a standard deviation of one.

Uniform Distribution: The uniform distribution is between a given range of data, where all outcomes are equally likely.

Exponential Distribution: The probability distribution between two random events occurring is calculated via the Exponential Distribution.

Poisson Distribution: Used to predict the number of occurrences of an event in a given time frame.

Bernoulli Distribution: A binary outcome distribution where the probability of success is p and the probability of failure is 1p.
Python comes with a SciPy library that makes it easier to work with such continuous probability distributions.
The library provides numerous functions representing these distributions. For example, if you want to plot a normal distribution in Python, you can use the numpy.random.normal function.
Conclusion
In this article, we explored Gamma Distribution, one of the most widely used continuous probability distributions in the statistical field. We learned about the shape and scale parameters of the Gamma Distribution and how to plot a Gamma Distribution in Python.
We also briefly covered some common distributions and their use in Python. By using these concepts, you can analyze the distribution of your data and make informed inferences.
To summarize, Gamma Distribution is a continuous probability distribution used in various fields, including actuarial science, engineering, and economics. It has two shape parameters and a scale parameter and can assume several shapes based on its alpha and beta values.
Python can be used to plot a single or multiple Gamma Distributions easily. Additionally, we covered some common probability distributions and how Python can be used to plot them.
By understanding these concepts and using them, you can analyze data and make informed decisions. As such, understanding Gamma Distribution and common probability distributions is vital for statisticians and data analysts across various fields.