Assignment 12

Investigation 12

 

Excel

This data set is based on the first class letter postage for the US Mail from 1933 to 1996. Plot the data and develop a prediction function. When will the cost of a first class postage stamp reach $1.00? when will the cost be 64 cents? how soon should we expect the next 3 cent increase?

 

Answer:

 

Given

 

Plotting the data:

 

As you can see, it is an exponential function.

Let’s find a function that best fits the data by selecting ‘add a trendline’ in Microsoft Excel to display the best fit function.

 

 

So, the function that best fits this set of data is

y = 2E – 33e0.0394x, where the x is the year and the y is the cost of a stamp (in cents).

 

When you add the current and future data to the data set above you get:

 

 

 

The cost of a first class postage stamp will reach $1.00 in the year 2028.  The cost will be $0.64 in the year 2017.  In 2010, we should expect a $0.03 increase according to our prediction equation.

 

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