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Estimating Methods, Variability, and Sampling for Drop-Test Data
To understand the variability between drops and within the experiment, replicate drops were made where the height, flow rate, speed, volume, and material dropped were constant. The effects of humidity, wind, and temperature were low enough to be assumed to be negligible. Basically, three drop types were tested with two replicates each (table 5).
| Summary of three drop types | |||||
|---|---|---|---|---|---|
| Drop tests | Height (feet) |
Speed (knots) |
Flow rate (gallons per second) |
Volume (gallons) |
Material |
| 201 and 202 | 150 to 160 | 131 | 250 | 900 | H2O |
| 203 and 204 | 145 to 160 | 130 to 133 | 250 | 871 to 877 | GTS-R |
| 205 and 206 | 155 to 160 | 133 to 137 | 500 | 821 to 958 | GTS-R |
The winds were equal to or less than 5 miles per hour, the temperature was between 70 and 90 °F, and the relative humidity was between 29 and 56 percent. Lids were placed on all the cups within 10 minutes, minimizing the liquid lost to evaporation.
The analysis of variance (ANOVA) results (appendix A) demonstrate how differences between factors can be compared. For instance, the mean continuous line length at 0.5 gpc for water is greater than the mean, continuous line length for GTS-R retardant (p-value of 0.000388). It also shows that the line length associated with the low flow rate of 250 gallons per second is longer at 0.5 gpc than the length associated with the high flow rate of 500 gallons per second (p-value of 0.0000955).
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