Probability Density Functions(PDF) and Comulative Density Function(CDF)
Probability Density Function(PDF): In simple wording, we can say this type of curves shows that how much percentage of data is present within a range with the help of histograms.
Let’s take an example with a graph:
- The Y-axis shows the percentage of the distribution
- The X-axis shows the range.
Question: How much percentage of distribution is between 0 to 2 which is shown on the x-axis.?
Answer: We can say 26 percentage of the data is present between the range 0 to 2 or we can say 74 percent of the data is not present between the range of 0 to 2.
The Probability density Functions are very useful for the analysis of the data.
Cumulative Density Function(CDF): It shows that at which percentage if the data less or greater then a particular data point or value.
Take a look at the below image.
On this Normal distribution, a line is showing. This line helps to indicate Cumulative Density Function. In this distribution on the y-axis, we have values between 0 to 1. It cannot above one because we know that our probability cannot exceed one it is always between 0 and 1.
How we can make this Line?
The CDF can be computed by summing these probabilities sequentially
We can understand CDF with some Questions.
Question 1: How much percentage of the data is less than 0?
Answer: 50% of the data is less than 0.
Question 2: How much percentage of the data is less than 2.
Answer 2: Approximately 98 percent of the data is less than 2.
Whenever we try to do this type of Analysis where we have to decide that how much percentage of the data is less than or greater than with respect to some value at the x-axis. There we have to use CDF.
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