Results 1 to 9 of 9

Math Help - Reasons why

  1. #1
    ADY
    ADY is offline
    Member
    Joined
    Oct 2007
    Posts
    188

    Reasons why

    Hey,

    I'm after a bit of advice.

    I have some data and its exponentially increasing by a growth factor of 1.618;

    Now im trying to think of two reasons as to why an exponential model would be more suitable than a linear model for my data?

    Any one help?

    Thanks

    ADY
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,325
    Thanks
    1296
    Quote Originally Posted by ADY View Post
    Hey,

    I'm after a bit of advice.

    I have some data and its exponentially increasing by a growth factor of 1.618;

    Now im trying to think of two reasons as to why an exponential model would be more suitable than a linear model for my data?

    Any one help?

    Thanks

    ADY
    I don't understand your question. You say it is "exponentially increasing". Why do you say that? Whatever your answer, that's a reason isn't it?

    If this is a homework problem and you are just "given" some data and asked to "give two reasons", obviously, the reasons will depend on the specific data.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Mar 2009
    Posts
    66
    Quote Originally Posted by ADY View Post
    Hey,

    I'm after a bit of advice.

    I have some data and its exponentially increasing by a growth factor of 1.618;

    Now im trying to think of two reasons as to why an exponential model would be more suitable than a linear model for my data?

    Any one help?

    Thanks

    ADY
    Well if it is growing by a constant factor each time it won't fit a linear model, since the amount it's increasing by keeps changing. In exponential models it increases by a constant factor, as in your data, and in linear it increases by constant amount, which clearly wouldn't fit here.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    ADY
    ADY is offline
    Member
    Joined
    Oct 2007
    Posts
    188
    ok so we have then the data:

    Time/wks - 1,  2,  3,  4,   5,   6,  7 (List 1)
    Toy ownership - 3,  5,  8, 13, 21, 33, 55 (List 2)

    I've used exponential regression when plotting the data, worked out the growth factor to be 1.618

    Now why would i use exponential model over linear?
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member
    Joined
    Mar 2009
    Posts
    66
    Quote Originally Posted by ADY View Post
    ok so we have then the data:

    Time/wks - 1,  2,  3,  4,   5,   6,  7 (List 1)
    Toy ownership - 3,  5,  8, 13, 21, 33, 55 (List 2)

    I've used exponential regression when plotting the data, worked out the growth factor to be 1.618

    Now why would i use exponential model over linear?
    Well...as you say, it's 'exponentially increasing'. Isn't that reason enough? A linear model wouldn't work.
    Follow Math Help Forum on Facebook and Google+

  6. #6
    ADY
    ADY is offline
    Member
    Joined
    Oct 2007
    Posts
    188
    so why is a exponential model more suitable than a linear model?
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by ADY View Post
    so why is a exponential model more suitable than a linear model?
    Plot the data, overlay the plot with the result of linear regression, and exponential. Is one better than the other?

    Alternativly compute the sum of square residuals for both fits to the data is one smaller than the other? With the residuals you could if you wish construct some sort of statistical test for the adequacy of the two models.

    CB
    Follow Math Help Forum on Facebook and Google+

  8. #8
    ADY
    ADY is offline
    Member
    Joined
    Oct 2007
    Posts
    188
    I think the answer is easier than i'm making out, i just cant seem to put down in words what they are after?

    Is it because an linear model doe not fit the data point accurately enough, and therefore an exponential model with regression creates a better picture of whats happening?
    Follow Math Help Forum on Facebook and Google+

  9. #9
    Senior Member
    Joined
    Jan 2009
    Posts
    296
    Yes and because using a liner model for exponential data would be plain stupid.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Reasons for two inclusions
    Posted in the Advanced Algebra Forum
    Replies: 3
    Last Post: June 5th 2011, 02:27 PM
  2. Replies: 1
    Last Post: September 28th 2010, 09:18 PM

Search Tags


/mathhelpforum @mathhelpforum