aydatabrizi Posted October 14, 2010 Report Share Posted October 14, 2010 I realize that this function could either be a power function, an exponential function, and a log function, and I have figured out a couple of equations for the power function, but I have no idea where to continue on from there. So guidelines and help would be much appreciated! Thanks. Reply Link to post Share on other sites More sharing options...
cotedazur Posted October 15, 2010 Report Share Posted October 15, 2010 what i dont understand is the second part of the portfolio when I'm asked "how well does your first model fit this new data?". The new data is the table illustrating the vertical G-force. Well, I don't know whether there's a mistake in my train of thoughts, but I think it is obvious that my previous model won't fit the new data because i calculated a function for horizontal and not for vertical ?! I'm confused, can anybody please help me?I realize that this function could either be a power function, an exponential function, and a log function, and I have figured out a couple of equations for the power function, but I have no idea where to continue on from there. So guidelines and help would be much appreciated! Thanks.Not sure, but why don't you graph your functions? Reply Link to post Share on other sites More sharing options...
ibHAMMER Posted October 16, 2010 Report Share Posted October 16, 2010 with the data given on my portfolio, using regressions on a ti-84, the power regression seems to work out the best. however, since it's not in our curriculum, many of my classmates stuck with exponential. how would you prove the power model algebraically?How did you guys get to the equation...?I just plotted it into Excel and grabbed the exponential function.Can someone explain to me why it isn't Power but it is Exponential?Power seems to fit even better too.And how would you derive that equation by hand...I also noticed someone talking about R-squared value... what is that?That is something that I am very confused with as well.What is the difference between a Power function and an Exponential function?the general formula is different.power: a(x^b)exponential: a(b^x) Reply Link to post Share on other sites More sharing options...
aydatabrizi Posted October 16, 2010 Report Share Posted October 16, 2010 I am fiddling with some numbers and trying to figure out the equations, but I can never get one that fits just right. Any tips/suggestions? And also, once I have figured out my equations, I am confused as to where to start the portfolio! Reply Link to post Share on other sites More sharing options...
ibHAMMER Posted October 16, 2010 Report Share Posted October 16, 2010 I am fiddling with some numbers and trying to figure out the equations, but I can never get one that fits just right. Any tips/suggestions? And also, once I have figured out my equations, I am confused as to where to start the portfolio!you should try reading the introduction and background, Ayda. -you know who this is Reply Link to post Share on other sites More sharing options...
music Posted October 17, 2010 Report Share Posted October 17, 2010 how would you explain the use of a power function?say, are there actual applications of the a and b in f(x)= ax^b?i honestly can't tell any true definition for the differences between a power and exponential function. Reply Link to post Share on other sites More sharing options...
cotedazur Posted October 17, 2010 Report Share Posted October 17, 2010 how would you explain the use of a power function?say, are there actual applications of the a and b in f(x)= ax^b?i honestly can't tell any true definition for the differences between a power and exponential function.My problem exactly, somebody help us please!!! Reply Link to post Share on other sites More sharing options...
Hexa Posted October 17, 2010 Report Share Posted October 17, 2010 For ax^b the slope is b and the y-intercept is the natural log of b. 1 Reply Link to post Share on other sites More sharing options...
cotedazur Posted October 18, 2010 Report Share Posted October 18, 2010 but how does this explain the use of a power function? Reply Link to post Share on other sites More sharing options...
Hexa Posted October 23, 2010 Report Share Posted October 23, 2010 The reason I put for using a power function was that if you take the data and plug it into a calculator, and then use diagnostic to find r, the power equation is the closest to one. Reply Link to post Share on other sites More sharing options...
cotedazur Posted October 30, 2010 Report Share Posted October 30, 2010 The reason I put for using a power function was that if you take the data and plug it into a calculator, and then use diagnostic to find r, the power equation is the closest to one.What do you mean by "use diagnostic to find r"? Sorryyy! And thank you sooo much. Reply Link to post Share on other sites More sharing options...
Henaline Posted October 30, 2010 Report Share Posted October 30, 2010 (edited) I think It cant be a power equation. It can be an exponential or logarithmic equation. exponential will have general equation y=ab^x. Logarithmic equation will be y= a + b lnX .how would you explain the use of a power function?say, are there actual applications of the a and b in f(x)= ax^b?i honestly can't tell any true definition for the differences between a power and exponential function.Power function is Y= a X^bexponential function is Y=a b^Xa, b are the constant which you can find out by substituting two points from the data in the equation . G-tolerance graph cant be power equation as the power equation is a parabola. Edited October 31, 2010 by Fizzy Dee Reply Link to post Share on other sites More sharing options...
Harry20larry Posted November 3, 2010 Report Share Posted November 3, 2010 having been set this, you could see that if there are only two constants (parameters) then the equation is undoubtably a power function y=ax^b.However, I have been told by my teacher to achieve full marks in this coursework the IB have said that you need to use 3 constants in your equation, since anyone can plug in values to excel and find an equation from it, which makes things a lot trickier.Does anyone even know where to start with 3 parameters? Reply Link to post Share on other sites More sharing options...
asian Posted November 5, 2010 Report Share Posted November 5, 2010 Does anyone know how to use Autograph to show plot the points (e.g. how to use a power regression etc..) Reply Link to post Share on other sites More sharing options...
Nadine6 Posted November 8, 2010 Report Share Posted November 8, 2010 Can someone help me in this IA?My model is the exponential function, however I want to find the parameters. I tried using Derive to solve the equations, but it doesn't work at all.Does anyone have an idea about how to solve exponential equations using Derive?!I would be really thankful if anyone could help, as the task is due next Thursday. Thank you in advance.Does anyone know how to use Autograph to show plot the points (e.g. how to use a power regression etc..)To plot the points on Autograph click on Data, and then choose 'Enter XY data set'.Regressions are only on GDC. Reply Link to post Share on other sites More sharing options...
haren Posted November 10, 2010 Report Share Posted November 10, 2010 For those of you who got an exponential or a logarithmic trend line on Excel, plot it as a scatter graph not a line graph and then the Power trend line will fit perfectly. Reply Link to post Share on other sites More sharing options...
irishc94 Posted November 13, 2010 Report Share Posted November 13, 2010 My teacher never explained limitations / implications of models. What does it mean in the simpliest terms possible? Please help Reply Link to post Share on other sites More sharing options...
sundayrose Posted November 19, 2010 Report Share Posted November 19, 2010 I was wondering if anybody has suggestions for alternative software or technology which I could use to model some data. I'm doing a practice G-force portfolio. I heard that excel also works. Does anyone also have any instructions for how I can do this? Thanks a lot! BTW, if anyone has any tips about writing a portfolio could you please tell me as well! ANYTHING would be helpful. Reply Link to post Share on other sites More sharing options...
Abdominal Procrastinator Posted November 19, 2010 Report Share Posted November 19, 2010 You can check the thread for graphing software if you don't want to use your graphing calculator. I've also heard of several online/computerized calculators. Excel is good for tables. That's about it. But for the G-Force Portfolio, you need to find the r values (correlation between modeled graph and given points) so you need some way of finding that. Reply Link to post Share on other sites More sharing options...
sundayrose Posted November 19, 2010 Report Share Posted November 19, 2010 Ok thanks a lot.Also just another general question, generally with portfolios when can you use technology and when do you have to hand solve?If it doesn't say 'using technology' then does that mean you must solve by hand or it is assumed that you will use technology for all the questions.Thanks- I'm quite confused... Reply Link to post Share on other sites More sharing options...
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