PRISMTC :: smarter statistical solutions - PRISMTC Tipsheets

Scoping Designs: 1 Introduction

When you have little knowledge of the factors, ranges, reproducibility of the process or measurement system, or of the results relative to the project goals, before committing time and materials to an experimental campaign consider using an economical minimum run scoping design to check the current experimental space.

A small carefully chosen set of baseline experiments will help to determine whether the equipment and method, together with the factors and ranges you have selected, are likely to achieve the desired goals repeatedly. Using typically just 4 experiments, run the process or method at:

the mildest conditions or settings
the most forcing conditions or settings
repeated centre point settings to provide a pure noise estimate and evidence of whether you are currently operating over an optimum

If it is unlikely you will achieve the goals, you can use the results of a scoping study to help you decide what to do next: add or drop factors; stretch or contract ranges to encompass or focus on an optimum region of your experimental space; follow up with a variation management study or measurement systems analysis due to excessive variation between the centre point results.

To handle scoping designs within the Statease Design Expert DX7^TM software tool, we have further tipsheets to help you:

Scoping Designs: 2 Building the Design
Scoping Designs: 3 Analysing and Interpreting your Results

These tipsheets are linked to this case study

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Top Spray Granulation Process

This Case Study is from pharmaceutical development and covers a series of designs that, when viewed together, illustrate the sequential nature of Design of Experiments (DoE). If you follow these designs through our tipsheets, you will also see how DoE can be successfully integrated into the activities of a Quality by Design (QbD) work flow.

The process developers identified a fluid bed top spray granulation process as the most appropriate commercial process type to manufacture a modified release tablet. A decision was then made about which parameters to Control; treat as Noisy, or eXperiment with (referred to as CNX). It was decided to investigate the effects of six input parameters: