What appears to be the relationship between a tornadoes width and it's intensity on the Fujita scale?

There is a general trend that tornadoes with a higher rating tend to be larger to the point that F0 and F1 tornadoes are generally fairly small while F4 and F5 tornadoes are usually very large.

However, this is not always the case. Some F4 and F5 tornadoes have been fairly small, and several enormous tornadoes have gotten F0 and F1 ratings.