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Interpreting and Curve Fitting Temperature Data

Activity Description Activity GuideTable


The chart below lists the average monthly temperatures for three cities in different parts of the world.

  Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr
Washington, DC 54 64 73 77 75 68 57 46 37 34 36 45 54
Verhoyansk, Russia 5 32 54 57 48 36 5 -35 -53 -57 -48 -25 5
Buenos Aries 63 55 48 50 52 55 59 66 72 73 73 70 63

Part 1: Plotting the Temperatures

(1) Observe the temperatures for Washington DC and describe their pattern over one year's time. Do the same for the other two cities. Make several interpretive statements about the data based on your observations.

(2) Enter all of the data (including the months as 1, 2, 3...) into a statistical list in your graphing calculator and draw a scatterplot of the Washington DC data. Reconcile the shape of this scatterplot with your earlier description and interpretive statements.

(3) Draw scatterplots of the data for the other two cities. Make several interpretative statements that compare and contrast the scatterplots for all three cities. Relate these statements to the geographical locations of the cities.

(4) Discuss the advantages of a visual representation for interpretation.

Part 2: Determining and Interpreting "best fit" Curves

(5) Discuss what type of curve would "best fit" the data.

(6) Write the general equation of the sine function [y = Asin(B(x+C))+D], and discuss the effect of each of the coefficients on the graph of the sine function. Discuss how these coefficients can be determined from the data given above.

(7) Determine a best fit sine curve for the Washington data incrementally, by determining one coefficient at a time and graphing the resulting curves. At each stage, observe the graph and compare your observations with your answers to Task 6.

  • First, use the maximum and minimum values of the distribution to compute the amplitude, A, for the best fit sine curve and graph y =Asin(x).
  • Next compute the vertical shift coefficient D, and graph y =Asin(x)+D.
  • Next adjust the period B [2/12], and graph y = Asin(Bx)+D.
  • Finally, estimate or compute the horizontal shift C, and graph the complete equation.

Discuss the fit of this curve.

Note: For Washington, y=21.5sin.52(x-1)+55.5; For Verhoyansk y=59sin.52(x-1)+1.7; and for Buenos Aires y=12.4sin.52(x+4.9)+61.4.

(8) Use your calculator to determine the least squares sine regression for this data. Compare your equation with the one generated by the calculator. (Note: some calculators display sine equations in the form Asin(Bx+C)+D)

(9) By referring to the coefficients for the Washington equation, estimate from the scatterplot, the A coefficient for the best fit curve for the Verhoyansk data. Next, do the same for the vertical shift coefficient, the period, and the horizontal shift coefficient. Graph the resulting equation. Discuss the fit of your curve.

(10) Revise your equations as needed to obtain a better fit, and discuss your revisions in relation to the scatterplot and numerical data. Graph your revised equation.

(11) Use your calculator to derive a least squared regression equation for Verhoyansk, and compare this equation to your revised equation.

(12) Repeat tasks 9, 10 and 11 for the Buenos Aires data.

(13) Discuss the relationships between the coefficients for the best fit equations for the three cities, and the geographical locations of these cities (e.g. hemispheres, latitude).

Extension 1: Oscillatory Data

Discuss other natural phenomena that have associated oscillating variables. Find two or three sets of oscillating data and determine best fit equations for them. Relate the coefficients of the best fit equations with physical aspects of the phenomena.

Extension 2: Green Globs

Open up the program Green Globs and play an expert game, using only sine equations. Discuss the differences between using the Asin(Bx+C)+D form and the Asin(B(x+C))+D form of the sine equation.




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Last modified on August 14, 2001.