Exponential Regression Model

Mathematics
Tutor: None Selected Time limit: 1 Day

Oct 2nd, 2015

Thank you for the opportunity to help you with your question!

In order to find the equation, you need to set up your lists for time and temperature.  It really depends on what kind of calculator you are using as to how you go about this.  All of them (besides the ti-83 and ti-84) have different steps, but they all do the same thing.  I can walk you through the calculator part if you need help setting that up, and where to go to find everything if you need me to, just let me know!  I can pretty much get you through any of them.  Find stat on your calc, and in your lists, use either list1 or c1 for the time, and list2 or c2 for the temperature.  Once you've done that, you're going to find the stat button again and set upturn on your plot, then you need to change the window to see the graph and the plots.  Make sure you use big enough numbers so that the entire graph will fit in the equation.  I have my window set up as xmin = 0,xmax = 75,xscl = 5, ymin=0, ymax=200, yscl= 10.  Then you want to get the equation, under stat, find regression, or depending on the calc, it'll say expreg.  Use that, then enter what you used for x (c1 or list1) and y (c2 or list2) and if your calc lets you, store the equation to y=, if not just write down the numbers they give you for a and b.  I got a = 171.461728 and b = 0.988247, so plug those numbers into the equation y = ab^x into your y= and graph it.  The graph should follow the plotted points pretty closely.  So it is a good fit.  To find part d, you can do this 2 ways... either set up the equation where y = 92, so you have 92 = 171.4617(.9882)^x and solve for x, this will give you x = 52.44 mins.  Another way you can do this is to use your trace function on the graph and find where y is closest to 92, which it'll show you between 52 and 53, so that goes along with solving the equation.  For part e, you can again solve the equation, but this time plug in the 65 for x instead of y, OR you can use the value button (when looking at the graph, press calc, then you should see value listed there, hit enter, and it'll ask x=? and press 65 and enter.  This will give you 79.5104. 

Please let me know if you need any clarification. I'm always happy to answer your questions. If you need any help with entering it in the calculator, or solving the equations, please let me know and I will walk you through how to do it on whatever calculator you are using, (Once you tell me which one that is :) Hope this helps!!!
Oct 2nd, 2015
Hello, thank you for helping me with this problem. However, I know this is bad but I do not have a graphinh calculator. I am in the military and am stationed overseas in a hazardous/combat zone. Could you elaborate more so that I can understand this answer more, without the use of a calculator? I know its much to ask, but I'm paying for this site so I might as well try to get as much out of it as I can! :D -Josh
Oct 4th, 2015

I understand your situation, and I will do the best I can to explain it without a calculator.  I'm not sure what type of access you have to the internet, but there are free downloads of the TI-83 graphing calculator that you can get, and they are relatively simply to use and understand.  They work just as well as the actual calculator, just may have a different look to it.  I am also working on my masters in accounting (glutton for punishment I guess as this is my second masters degree).  I have an exam today that I have to prepare for,but take a look at the downloadable graphing calculators (and don't get suckered into paying for one, there are perfectly fine free ones available.  Let me know if you get one, or when you do, and I can help you through setting it up on the calculator online.  Since this problem deals with exponential regression, you will have too many decimals to deal with trying to calculate all of this by hand, but I can definitely walk you thru the theory so you understand what to do for these types of problems, if for some reason you can't download one.  Best of luck over there!

Oct 4th, 2015

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