What exactly is the difference bet. a CDF and a PDF?

In summary, the PDF (Probability Density Function) is a single formula that describes the probabilities for a given distribution, such as the binomial distribution in the example of tossing a coin. It is different from simple probability because it provides a more comprehensive and efficient way of calculating probabilities for a range of outcomes. The CDF (Cumulative Distribution Function) is the sum of probabilities and is another way to represent the distribution. The PDF is not always based on the binomial distribution, it depends on the specific distribution being analyzed.
  • #1
Peon666
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Homework Statement



I understand that PDF is a derivative of CDF and hence CDF is the integral of PDF. But I don't understand the difference between PDF and simply probability? What exactly is the differece? What extra things does PDF tell us which simple probability does not?

Homework Equations



For example, we toss a coin and a head comes. Probability of it is 1/2. What's PDF in this case?

The Attempt at a Solution

 
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  • #2
Well say you toss a coin 1000 times and you want the probability of exactly 3 heads. To write down all the possibilities, would take a long time. The pdf is basically a single formula that would describe the probabilities. So for the coin toss (it follows a binomial distribution)
P(X=3)= 1000C3(1/2)3(1/2)1000-3

A cdf sums the probabilities.


EDIT: that is for a discrete distribution
 
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  • #3
I think I'm getting to the idea but I'm not completely clear yet. I understand the difference between CDF and PDF but what's the difference between simple probability and PDF?

And do we always follow the binomial distribution in PDF?
 

1. What is a CDF?

A cumulative distribution function (CDF) is a function that shows the cumulative probability of a random variable being less than or equal to a given value. It can be thought of as the running total of probabilities up to a certain point.

2. What is a PDF?

A probability density function (PDF) is a function that shows the relative likelihood of a random variable taking on a specific value. It represents the probability distribution of a continuous random variable.

3. What is the main difference between a CDF and a PDF?

The main difference between a CDF and a PDF is that a CDF shows the cumulative probability of a random variable being less than or equal to a given value, while a PDF shows the relative likelihood of a random variable taking on a specific value.

4. When would you use a CDF vs a PDF?

CDFs are often used to determine the probability of a random variable being within a certain range or above/below a certain value. PDFs, on the other hand, are often used to determine the likelihood of a random variable taking on a specific value.

5. Can a CDF and a PDF be used interchangeably?

No, a CDF and a PDF cannot be used interchangeably. They represent different aspects of a probability distribution and have different mathematical properties. However, they are related and can be used together to fully describe a probability distribution.

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