Statistics

• How Many Times Should an Experiment Be Repeated?
  There is no universal number of experimental repetitions. Plan the sample size from your desired precision or statistical power and expected variability.
• Are Credit Card PINs Qualitative Ordinal Data?
  A credit card PIN is nominal categorical data, not ordinal: its digits form an identifying code with no meaningful ranking or arithmetic.
• How to Calculate the Detection Limit
  Calculate an analytical detection limit from response variability and calibration slope, and learn when the common 3.3σ/S estimate is appropriate.