20. A number of studies have shown lichens (certain plants composed of an alga and a fungus) to be excellent bioindicators of air pollution. The article “The Epiphytic Lichen Hypogymnia Physodes as a Biomonitor of Atmospheric Nitrogen and Sulphur Deposition in Norway” (Envir.

Monitoring and Assessment, 1993: 27–47) gives the following data (read from a graph) on x
NO

3 wet deposition

(g N/m2

) and y
lichen N (% dry weight):

The author used simple linear regression to analyze the data.

Use the accompanying MINITAB output to answer the following questions: