## 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.

## Science Librarian |

Contact InfoMark O. Hatfield Library 900 State Street, Salem Or 97304 503-370-6525 jrepplin@willamette.edu Send Email |