Explorations with spreadsheets

 

By: Diana Brown


This exploration is from data that is based on the first class letter postage for the US Mail from 1933 to 1996.


The Data

 

year

rate(in cents)

1919

2

1932

3

1958

4

1963

5

1968

6

1971

8

1974

10

1975

13

1978

15

1981

20

1985

22

1988

25

1991

29

1994

32

1997

33

1999

34

2002

37


The Graph of the data using Microsoft Office Excel

 

Notice the graph looks like an exponential function.

 

Here is a graph of the data with a predicted function and equation when I created the best fit equation

 


 

Some predictions for the future:When will the cost be 64 cents? When will the cost of a first class postage stamp reach $1.00?How soon should we expect the next 3 cent increase?

 

Letís extend the data in the table using the equation from above:

 

year

rate(in cents)

1919

2

1932

3

1958

4

1963

5

1968

6

1971

8

1974

10

1975

13

1978

15

1981

20

1985

22

1988

25

1991

29

1994

32

1997

33

1999

34

2002

37

2003

37

2004

39

2005

40

2006

42

2007

43

2008

45

2009

47

2010

49

2011

51

2012

53

2013

55

2014

57

2015

59

2016

62

2017

64

2018

66

2019

69

2020

72

2021

75

2022

78

2023

81

2024

84

2025

87

2026

90

2027

94

2028

98

2029

101

 

Notice that in the year 2017 the price of stamps will be around 64 cents and around 2029 the price will be $1.00.

 

The graph of the extended data

 


Click Here for Excel Spreadsheet File


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