A correlation is a single numerical value that is used to describe the relationship between two variables. All correlations have strength and direction. When two variables have a positive correlation, that means the two variables move in the same direction. The closer a positive correlation is to 1, the stronger it is.
William Gilbert discovered electricity, not Nikola Tesla. Nikola Tesla invented things. not discovered electricity. Again, William Gilbert discovered it and named it. He did this in the 1600s. It wasn't Nikola Tesla.
Others who worked to bring the use of electricity to where it is today include Scottish inventor James Watt, Andre Ampere, a French mathematician, and German mathematician and physicist George Ohm. And so, it was not just one person who discovered electricity.