A laboratory receives a seizure of 592 kilogram "bricks" of white powder. All appear to be similar based on physical characteristics. The laboratory has tested many such seizures in the past months and all have been shown to be cocaine. Use the ENFSI spreadsheet to determine how many samples must be initially tested to show that 90% of the seizure contains cocaine with 95% confidence.

Question

Quizplus · Accepted Answer

Using the ENFSI spreadsheet:

- Population size: 592 kg = 592,000 g
- Expected variability: 50%, as we do not know the exact proportion of cocaine in the seizure
- Confidence level: 95%
- Confidence interval: 10% (90%-100%)
- Margin of error: 5%

The spreadsheet results show that we need to test at least 28 samples to have a 95% confidence that 90% of the seizure contains cocaine, with a margin of error of 5%. Therefore, the answer is choice C.

A Laboratory Receives a Seizure of 592 Kilogram "Bricks" of White