The mean (the average) is the sum of the values divided by how many there are. The median has half the data below it and half above. The mode is the value that appears most often, and there can be more than one. When data are lopsided (skewed), a few extreme values pull the mean toward the long tail, so all three typical values can be useful. An X-Y plot can show a positive relationship, but a correlation does not prove that one thing causes the other; more research, often from other sources, is needed.