Correlation. Correlation. Definition: the degree of relationship between two or more variables. For example, smoking and lung cancer are correlated:
PowerPoint Slideshow about 'Correlation' - tamarr
An Image/Link below is provided (as is) to download presentation
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
If your two variables are positively correlated, many of the X scores with positive z-scores will be paired with Y scores with positive z-scores. And many X scores with negative z-scores will be paired with Y scores with negative z-scores.
If you multiply two positive numbers or two negative numbers, you will get a positive number. If you have a whole bunch of positive products and add them up, you will get a large positive number.
The reverse could be true: the more firefighters fighting a fire, the bigger the fire is, so do firefighters cause fires to be larger?
They might both cause each other: exercising causes someone’s health to improve, which is influential in their exercising more (because they “feel like it”)
They might both be caused by another variable: Falling asleep with one’s shoes on is correlated with waking up with a headache, but these are both caused by getting completely blitzed the night before.
Complete coincidence: for example, the number of churches in the U.S. has been rising steadily and so has the average global temperature (but there may actually be a better explanation for this example).