posted by gandakho on .
The brightness of sunlight at the earth's surface changes over time depending on whether the earth's atmosphere is more or less clear. Sunlight dimmed between 1960 and 1990. After 1990, air pollution dropped in industrial countries. Did sunlight brighten? Here are data and scatterplot from Boulder, Colorado, averaging over only clear days each year. (Other locations show similar trends.) The response variable is solar radiation in watts per square meter.
Year 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002
Sun 243.6 245.4 247.4 250 250.9 250.1 250.5 249.6 251.3 251.3 251.3
Has sunlight dimmed overall?
What is the best word to describe the type of relationship?
What is the correlation between the year and sun brightness (round your answer to at least two decimal places.)