Results 1 to 4 of 4

Math Help - regression

  1. #1
    Junior Member
    Joined
    Jul 2007
    Posts
    30

    regression

    I do not even know where to begin with this problem...please help. I am in intermediate algebra, summer session, which is moving quite fast. It seems as if there is no time for understanding.

    Please explain how would I know when to use log in the equation when I have a word problem and it is only asking to find an equation for f.

    Also what is the base b of the function f(t)= ab^t?

    How do I find regression equations?

    Please help, I have a test on Tuesday.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by getnaphd View Post
    I do not even know where to begin with this problem...please help. I am in intermediate algebra, summer session, which is moving quite fast. It seems as if there is no time for understanding.

    Please explain how would I know when to use log in the equation when I have a word problem and it is only asking to find an equation for f.

    Also what is the base b of the function f(t)= ab^t?

    How do I find regression equations?

    Please help, I have a test on Tuesday.
    First try to put only one question in a post, you can post any number
    seperatly.

    Second, can you give n example of the type of word problems you have.

    Third, b is a constant in the equation which is raised to the variable power t.

    Fourth. look here.

    RonL
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Jul 2007
    Posts
    30

    summer college math...help

    Sorry for the many questions..I was frustrated and up late. Still I have had no sleep.

    Here is an example:Before 1997, the Library of Congress sold copies of its 3x5 catalog cards to other libraries. Due to libraries using computer catalogs, the Library of Congress stopped selling such cards in March 1997. The number of cards sold (in millions) for various years are listed in the table below.

    Year Number of Cards Sold (in millions)
    1971 74.47
    1976 39.82
    1981 15.64
    1986 8.08
    1991 2.36
    1996 0.57

    Let f(t) represent the number of cards in millions in the year that is t years since 1970.


    a) Find an equation for f.
    b) Use your model to estimate the number of cards sold in 1960.
    c) What is the base b of your model f(t)=ab^t? What does it mean in terms of the situation?

    Thanks
    Last edited by CaptainBlack; July 8th 2007 at 11:51 AM. Reason: Post the correct question
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Grand Panjandrum
    Joined
    Nov 2005
    From
    someplace
    Posts
    14,972
    Thanks
    4
    Quote Originally Posted by getnaphd View Post
    Sorry for the many questions..I was frustrated and up late. Still I have had no sleep.

    Here is an example:Before 1997, the Library of Congress sold copies of its 3x5 catalog cards to other libraries. Due to libraries using computer catalogs, the Library of Congress stopped selling such cards in March 1997. The number of cards sold (in millions) for various years are listed in the table below.

    Year Number of Cards Sold (in millions)
    1971 74.47
    1976 39.82
    1981 15.64
    1986 8.08
    1991 2.36
    1996 0.57

    Let f(t) represent the number of cards in millions in the year that is t years since 1970.


    a) Find an equation for f.
    b) Use your model to estimate the number of cards sold in 1960.
    c) What is the base b of your model f(t)=ab^t? What does it mean in terms of the situation?

    Thanks
    You are going to do a power law fit. The model is of the form:

    <br />
f(t)=a~b^t<br />

    Now we know how to do linear regerssion so we want to convert this lo a linear model, so we take logs to get:

    <br />
\log(f(t))=b \log(t)+log(a)<br />

    so we put \tau = \log(t), F(\tau)=\log(f(e^t)), and [tex]\alpha=log(a) , which gives us the linear model:

    <br />
F(\tau)=b\ \tau + \alpha<br />

    and take logs of the data in the table, and we have a bog standard linear regression problem.

    RonL
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Ncaaf multiple regression/ stepwise regression
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: August 10th 2011, 07:21 AM
  2. Regression SS in multiple linear regression
    Posted in the Advanced Statistics Forum
    Replies: 0
    Last Post: June 20th 2009, 01:23 PM
  3. regression help
    Posted in the Advanced Math Topics Forum
    Replies: 1
    Last Post: October 15th 2008, 12:25 AM
  4. Regression
    Posted in the Advanced Statistics Forum
    Replies: 5
    Last Post: February 18th 2008, 07:46 AM
  5. Help with Regression
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: December 7th 2007, 05:56 AM

Search Tags


/mathhelpforum @mathhelpforum