Research Guides: MATH 141: Calculus I: Assignment

QUAD Center

Center for Quantitative Understanding, Analysis, and Design (QUAD Center)

The QUAD Center focuses both on the kinds of basic mathematics central to academic and civic literacy and on research design and statistical issues arising in a broad range of disciplines across the liberal arts. This emphasis complements extensive expertise related to calculus and more advanced mathematical topics already available through the Mathematics Department.

Center Hours

Mon 10:30am-12:30pm, 2:30-4:30pm

Tue 12-2pm, 4:30-6:30pm

Wed 9:30-11:30am, 7-9pm

Thu 9:30-11:30am, 2-4pm, 6-8pm

Fri 11:30am-1:30pm

Locate Data Sets

READ THIS FIRST

Locating reliable data sets can be very difficult. One of the best resources for finding data sets is the U.S. government; it collects and maintains huge amounts of data on a variety of topics (click here for an A-Z list of government depts). The government typically waits for the calendar year to end before publishing data. When you see data that appears to be a year or so old, this may actually be the most current data available.

Most studies use annual government data, but some researchers perform their own studies to get data. This is where I come in. If you need more current data or on a topic that is not included in this guide, contact John Repplinger via email.

To begin locating statistical data, consider which part of the government would contain the data. The tabs above link to data sets you can use for this assignment. They list where the data comes from, so you can find their original source, and explore similar data.

Excel 2007 Directions

Basic curve fitting with Excel 2007

(Based from: http://www.ithaca.edu/tpfaff/pdf/CurveFittingWithExcel2007.pdf)

1. DATA
There must be two columns of data. One column of X (input, predictor, independent) data, and one column of Y (output, response, dependent) data. The size of both data sets must be the same.

2. SCATTER PLOT
First highlight the input x and output y data by holding the left mouse button down. If the x and y data columns are not adjacent then highlight the x data while holding down the control key, lift your finger over the left button after the x data is highlighted and then highlight the Y data. Once this is done go to Insert Scatter and choose the first option which is a simple scatter plot. To label axis click on the scatter plot and then go to Design Chart Layouts and choose the left most option (or really whichever one you like but this will do). You can now right click on the labels to edit them.

3. FITTING A MODEL
First be sure that your chart is highlighted (left click on the chart anywhere if it isn't). Go to Layout Trendline. Be sure to choose more trendline options. As you click different curves you will see the curve on the scatter plot. You have 6 options and note that when selecting polynomial you need to set the order of the polynomial (2 is quadratic, 3 is cubic). At the bottom of the Format Trendline box choose Display Equation and Display R squared. Note also that you can choose to give the equation a name, choose to have the equation extrapolated forward or backward, and set a fixed intercept value.

Curve Fitting with Excel (1997-2003)

(Based from: http://www.ithaca.edu/tpfaff/pdf/CurveFittingWithExcel.pdf)

1. DATA
Data There must be two columns of data. One column of "x" (input, predictor, independent) data, and one column of "y" (output, response, dependent) data. The size of both data sets must be the same.

2. SCATTER PLOT
First highlight the input x and output y data by holding the left mouse button down. If the X and y data columns are not adjacent then highlight the x data while holding down the control key, lift your finger or the left button after the x data is highlighted and then highlight the y data. Once this is done go to Insert Chart. In the dialog box choose scatter plot and follow your way through by clicking next. In step 3 of the cart wizard you should label your axes and give the chart a title. In step 4 you have the option of putting the graph in as a new sheet (you will get a larger graph to view and is often helpful when making more than one graph) or as an object in a worksheet -recommended- (your graph will be small but in the same worksheet as the data set, this is good if you only want a couple of graphs from a given worksheet).

3. FITTING A MODEL
First be sure that your chart is highlighted (left click on the chart anywhere if it isn't). Go to Chart & Add Trendline. You have 6 options. Note that when selecting polynomial you need to set the order of the polynomial (2 is quadratic, 3 is cubic). Before clicking Ok, go to the option tab and check Display Equation and Display R squared. Note also that under options you can choose to give the equation a name and you can choose to have the equation extrapolated forward or backward.

SOME OPTIONS AND DETAILS
² Changing Axis Range To change the range on a particular axis (say the x-axis) you need to first click on the axis so that in the upper left corner it says Value (X) axis. Now go to format & selected Axis or Ctrl 1. In this dialog box click on the scale tab and set the range.

² Forecasting You can extend the model (trendline) forward or backward beyond the data set: Right click on the trendline and go to format trendline. Under the options tab and adjust the forecast value forward or backwards.

² Setting the decimal places in a model Once a trendline has been added to a graph you may need to add decimal places to the equation, especially if excel starts using scientic notation (signicant digits are often lost when excel does this). Right click on the equation you want to change and select Format Data Labels. Choose the Number tab and go under Number in the Category. A box will appear to set the desired number of decimal places. As a rule it seems safe to go one more decimal place than needed to get rid of the scientific notation.