 Hi everyone, it's MJ and welcome to the introductory video on joint distribution functions. By now you should be quite comfortable with this image which tries to explain all the statistics in a nutshell. And what I want to do here is look at this component called data. Because before this we have been assuming that all of the data has been the result of a single random variable. However in this course what we're going to see is that data can come from multiple random variables. And this does confuse the math, well when I'm confused it does make it a little bit more complicated because these random variables here also have their own set of parameters and distributions. And what we're going to be trying to do in this course is by seeing that we can combine the distributions together and we can get something like marginal distributions, we're going to get conditional distributions and we're very interested in the link between the random variables that are combining together to make our data. And one of the big concepts is this idea called correlation. Correlation is a dimensionless quality to try and show what the linear relationship is between these random variables. One thing that many people sometimes make a mistake in is that they think correlation causes causation. And the classic example with correlation not being the case is they found that the length of someone's arms and their IQ or their maths ability were linked. So people who had longer arms were smarter when it came to maths abilities, they found that there was a very strong correlation. However, someone pointed out that this wasn't necessarily causation, long arms aren't causing better maths ability. What was actually happening was there was a hidden variable called age which as people getting older so their arms were getting longer and their maths ability was increasing and this is age for children. So there is some of the things you have to pick up and you can't just blindly apply the maths and say oh I found the link of correlation and we can now use that to influence our insurance strategy or how we tackle financial markets. So you do need to think a little bit behind the statistical concepts that we are introducing but this course does look at the relationship between multiple random variables that are coming together to create a data set for us. Anyway, I'll see you guys in the rest of the course. Keep well. Cheers.