Model Browser User's Guide

Optimal Design: Start Point Tab

The Start Point tab allows you to define the composition of the initial design: how many points to keep from the current design and how many extra to choose from the candidate set.

1. Choose the type of the optimal design, using the Optimality Criteria drop-down menu:

• D-Optimal designs -- Aims to reduce the volume of the confidence ellipsoid to obtain accurate coefficients. This is set up as a maximization problem, so the progress graph should go up with time.

• The D-optimality value used is calculated using the formula

where X is the regression matrix and k is the number of terms in the regression matrix.

• V-Optimal designs -- Minimizes the average prediction error variance, to obtain accurate predictions. This is better for calibration modeling problems. This is a minimization process, so the progress graph should go down with time.

• The V-optimality value is calculated using the formula

• where x_j are rows in the regression matrix, X_C is the regression matrix for all candidate set points and n_C is the number of candidate set points.

• A-Optimal designs -- Minimizes the average variance of the parameters and reduces the asphericity of the confidence ellipsoid. The progress graph also goes down with this style of optimal design.

• The A-optimality value is calculated using the formula

• where X is the regression matrix.

2. You might already have points in the design (if the new design node is a child node, it inherits all the properties of the parent design). If so, choose from the radio buttons:
• Keep current design points
• Keep current fixed design points
• Do not keep any current points
3. Choose the number of additional points to add by clicking the Optional Additional Points up/down buttons or by typing directly into the edit box.

Creating an Optimal Design

Optimal Design: Candidate Set Tab