Week 11 - Scatter Plots

Bivariate Data

Bivariate data refers to two varialbes - so it's in the name, "bi" meaning two and "variate" referring to our variables. In this section, we want to compare to variables and see if there is a relationship between them. We then want to describe what time of relationshop they have. For example, we might be interested in knowing, do taller people generally have heavier school bags?

Correlation Versus Causation

Just because two sets of data appear to have a relatioship, doesn't mean they actually have anything to do with eachother. Check out the video below about the difference between correlation and causation. Then check out the following site that shows some funny correlations - just coicidences in data. 

Describing a Trend from a Scatter Plot

We tend to display bivariate data in a scatter plot. Each dot in the scatter plot represents one person's data. Based on how the data lines up, you will be able to describe the trend of the bivariate data. We talk about two things:
Strength: Very weak, weak, moderate, strong, very strong
Direction: Positive or negative
Check out these examples below to get an idea:

Using CODAP to create a Scatter Plot and Line of Best Fit

Statistics Test Revision