When we have bivariate data, we want to determine what sort of relationship the two variables have. As the independent variable ($x$x-axis) changes notice how the dependent variable ($y$y-axis) tends to change. Just by observation, we may notice the following:
Even when two variables have a relationship, it may not be a causal relationship. We cannot say for sure that a change in the value of $x$x causes $y$y to change or that the value of $y$y causes a corresponding value of $x$x even when a relationship is apparent. It may be that both $x$x and $y$y have a relationship with some other hidden variable, which creates an indirect relationship between $x$x and $y$y.
The scatter plot shows the relationship between sea temperature and the amount of healthy coral.
Which variable is the dependent variable?
Which variable is the independent variable?
The scatterplot shows the height and weight of six students. Use the plot to answer the questions.
How tall is the student who weighs $45$45kg?
How tall is the tallest student?
The price of ten houses is graphed against the house's land area below.
Describe the relationship between land area and house price in the data.
Use scatter plots to investigate and comment on relationships between two numerical variables
Investigate and describe bivariate numerical data where the independent variable is time.