Table I.
Factors in the Plackett–Burman Screening Design
| Code | Low level | High level | |
|---|---|---|---|
| Independent factors | |||
| Poly (ethylene oxide) molecular weight | X 1 | 6 × 105 | 7 × 106 |
| Poly (ethylene oxide) amount (mg) | X 2 | 100.00 | 300.00 |
| Dummy | X 3 | −1.00 | 1.00 |
| Ethylcellulose amount (mg) | X 4 | 0.00 | 50.00 |
| Drug solubility (mg/mL) | X 5 | 9.91 | 136.00 |
| Drug amount (mg) | X 6 | 100.00 | 200.00 |
| Sodium chloride amount (mg) | X 7 | 0.00 | 20.00 |
| Citric acid amount (mg) | X 8 | 0.00 | 5.00 |
| Polyethylene glycol amount (mg) | X 9 | 0.00 | 5.00 |
| Dummy | X 10 | −1.00 | 1.00 |
| Glycerin amount (mg) | X 11 | 0.00 | 5.00 |
| Dependent factors | |||
| Time to release 90% of the drug | Y 1 | ||
| n value | Y 2 | ||
| % amount released in 4 h | Y 3 | ||
| % amount released in 8 h | Y 4 | ||