The relationship of two variables

Statistical Techniques in Tableau

Maarten Van den Broeck

Content Developer at DataCamp

Revisit the lake again

Revisit the lake again: scatter plot

• Variable of interest is placed on y-axis

Correlation coefficient

• Quantifies the relationship between two variables
• Between -1 and 1
• Sign (+ or -) corresponds to direction of relationship
• Magnitude (absolute value) corresponds to strength of the relationship

Trend lines

• Visualizes the relationship between two variables
• As close as possible to each data point
• A high (absolute) correlation value has all point close or on the trend line
• Not necessarily a straight line

Trend lines: linear vs. logarithmic

Linear trend line

Logarithmic trend line

Trend lines: predicting and extrapolating

• Distance of 1400 m corresponds to approx. 19 species

• Distance of 3000 m corresponds to approx. 21 species

Other types of trend lines

• Exponential: inverse of logarithmic
• Power or log-log: both variables follow logarithmic trend
• Polynomial: n-degree, from second degree till eight degree

Let's practice!

Statistical Techniques in Tableau