# Thread: Identifying symbol for the likelihood for linear regression.

1. ## Identifying symbol for the likelihood for linear regression.

What is that weird symbol (boxed in pink in the screenshot below) called? I'd like to know the name so I can learn more about it on YouTube. Thanks!

3. ## Re: Identifying symbol for the likelihood for linear regression.

it's called Capital Pi notation. It stands for the product of all of the indexed terms. For example

$n! = \prod \limits_{k=2}^n~k$

4. ## Re: Identifying symbol for the likelihood for linear regression.

Originally Posted by asilvester635
What is that weird symbol (boxed in pink in the screenshot below) called? I'd like to know the name so I can learn more about it on YouTube. Thanks!
Surely you know that $\sum\limits_{k = 1}^9 k =45$ represents the sum of the integers one to nine.
The symbol $\sum$ is the capital Greek letter sigma for sum.

Well $\prod\limits_{k = 1}^9 k = 362880$ is the product of the integers one to nine.
The symbol $\Pi$ is the Greek letter capital pi for product.