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Tutorial #1: Create the Design

The first step in DOE PRO is to create the design. For our catapult experiment we are going to use the Computer Aided function in DOE PRO to help us choose our design. We know that we have 3 factors and we want to use a 3 level design so we can investigate quadratic effects.

  • From the Excel menu bar choose "DOE PRO" - "Create Design" - "Computer Aided…".
  • At this point DOE PRO needs to know how many levels are in our design. Since we have already decided that we want to investigate quadratic effects, we will choose by clicking on the "3 Level Design" option in the "Number of Levels" group (see below). We will also click on "Quantitative Only " in the "Type Factors" group. In the main area we will click on "3 Factors (3 Factor CCD or BB)" because we have 3 factors. Finally, we can choose from either a Central Composite Design (CCD) or a Box-Behnken; click on "Central Composite" in the "Choose Design Type" group. Click on "Next >>" when done (your window should look just like the one below).

Computer Aided Design Selection window

  • Since we chose a CCD, we need to indicate how many center points and what alpha value we would like to use. In this case, we will use two center points and an alpha value of 1.0. Click "Next >>" when done (your window should look just like the one below).

Axial and Center Points

  • Now we need to name our factors and define the high and low values for the DOE. The factor names, highs and lows are listed below. Note that we only type numeric values in for low and high (i.e., we type "160" not "160 Degrees").
 NameLowHigh
 Pull Back Angle160 (Degrees)180 (Degrees)
 Stop Angle24
 Cup Angle0 (Degrees)90 (Degrees)
    Type this information in the window and press the "Next >>" button when done (your window should look just like the one below).

Name, low, and high window

  • We now need to tell DOE PRO how many responses and replications we have. Since we have two outputs (the distance the red ball and the green ball travel) we need to select "2" under the option "How many responses do you have?". Since we only have enough time to do two replicates, we will select "2" under the option "How many replications would you like?". Click the "Next >>" button when done (your window should look just like the one below).

Number of replicates

  • DOE PRO will now ask us for the response names. This step is optional, however, it really helps to name the responses for ease of analysis, so we will name them "Red Ball" and "Green Ball". Type this information in the window and press the "Finish >>" button when done (your window should look just like the one below).

Response Names

  • At this point, DOE PRO is going to create our design for us and give us a place to type in our outputs (dependent data). Our outputs are the distances the red and green ball travel for each combination of inputs. The actual distance data for the Green ball and the Red ball are shown below.
  • How did we get this data? We had to do experimentation (thus the title Design of Experiments). For the first row, we set the Catapult at a Pull Back Angle of 160 Degrees, a Stop Angle of 2, and a Cup Angle of 0 Degrees. We then loaded up the green and red balls and shot them. The red ball traveled 32 inches and the green ball traveled 31.5 inches. We did this for every run and replication in the design. Red Ball Data
design matrix red ball
Green Ball Data
design matrix green ball

We have now created our design and performed the experiment. The next phase is analysis.