Scatter Graphs & Correlation Flashcards

All 6 cards in this deck

What does a scatter graph show?

The relationship between two variables measured for each item (bivariate data), with one variable on each axis.

What are the steps to plot bivariate data on a scatter graph?

e.g. a student scored 34 in Science and 38 in Maths, with Science on the $x$-axis

1. Take the first variable as the $x$-value: $x = 34$
2. Take the second variable as the $y$-value: $y = 38$
3. Mark a cross at that point: a cross at $(34, 38)$

What type of correlation is shown when one variable decreases as the other increases?

Negative correlation.

e.g. as rainfall increases, hours of sunshine decrease.

On a scatter graph, what does it mean to say the correlation is strong?

The points lie close to a straight line.

Weak correlation means the points are more spread out from a line.

What is an outlier on a scatter graph, and how do you write down your answer when asked to identify one?

A point that does not fit the trend of the other points (far away from the others); write it as coordinates, e.g. $(10, 19)$.

True or false? A scatter graph showing positive correlation between ice cream sales and numbers of sunburn cases proves that eating ice cream causes sunburn.

False. Correlation does not indicate causation — another factor (hot, sunny weather) could be affecting both.