Homework 6: Linear Functions and Trendlines
ISP 120

1.  The function T depicted in the table below gives the air temperature, in degrees Celsius, of air at altitude a (in meters above sea level), assuming stable air and a temperature of 21° at sea level:

a	T
0	21
1500	7
3000	-7
4500	-21

a. Determine if the above table represents a linear relationship.  If it is linear, express the relationship as an equation.  (When calculating the slope (average rate of change), show 5 decimal places.)

b. What would you expect the air temperature to be at an altitude of  5500 meters?

c. At what altitude would you expect the air temperature to be - 40°?

d.  Commercial airplanes fly at altitude of about 30,000 feet (9,144 meters) above sea level.  Using your function, calculate the air temperature outside a commercial airliner flying at this altitude. 

2. Open the file USTobacco_2004.xls which contains data on the total amount of tobacco produced in the US.

a. Make an XY scatter plot of the data. Include it in your document.

b. Add a linear trendline to your plot, including the equation and the R-squared value. Include it in your document.

c. Use the equation in b. to predict the amount of tobacco produced in 2012.

d. How much confidence do you have in your prediction? Why?

3.  Open the file Smoking_2002.xls which contains data on the percent of the US adult population that smokes cigarettes.

a. Make X,Y scatter graph of the years and the total percentages (not male and female) and add a trendline.  Include the equation and R-squared value for the trendline.  Paste the resulting chart into your Word document.

b. Using your model (trendline), predict the percentage of the total  population that smokes in 2008. How much faith do you have in your prediction?

c. Use your model to estimate what percentage of the total population smoked in 1953.  How much faith do you have in your prediction?

d. Use your model to estimate when 100% of the US population smoked.  How much faith do you have in your prediction?  Explain.