From 11:00PM PDT on Friday, July 1 until 5:00AM PDT on Saturday, July 2, the Shmoop engineering elves will be making tweaks and improvements to the site. That means Shmoop will be unavailable for use during that time. Thanks for your patience!
This is a scatter plot showing the amount of sleep needed per day by age.
As you can see, as you grow older, you need less sleep (but still probably more than you currently are getting...).
What type of correlation is shown here?
Estimate a line of best fit.
Using this line, predict how many hours of sleep a 22 year old needs.
Using this line a 22 year old needs about 7.5 hours of sleep.
Using this line, predict how many hours of sleep a 6 month old child needs.
Using this line a 6 month old (½ year old) needs about 14.5 hours of sleep a day. This is probably less than needed, but it's generally in the ballpark.
Can we use this line to predict how much sleep a 40 year old needs?
Since this data is not quite linear (i.e., falling in a straight line) if we use it to predict ages outside the range provided, it will probably be inaccurate. If we extend both axes, here is what this line would predict for a 40 year old:
Obviously, a 40 year old needs more that 2 hours of sleep/day. This is an example of when we cannot use this graph to make a prediction.
These two scatter plots show the average income for adults based on the number of years of education completed (2006 data). 16 years of education means graduating from college. 21 years means landing a Ph.D.
What type of correlation does each graph represent?
Both graphs are positively correlated. As years of education increase, so does income.
Draw a line of best fit for each graph then estimate and compare the earnings for each gender with 11 years of education completed.
Based on these plots it looks like a female who completes 11 years of school can expect to earn around $14,000/year while a male can expect to earn around $23,000/year.
These graphs show two important things. First, higher education does lead to a higher income in general. Second, there is a gender gap in income. While women have begun to close this discrepancy, there is more work to do.