Probability Fundamentals - Briliant Course

• The population of Derry is 10K
• There are 95% chances that Nick is flu-free
  • Sick: 500
  • Healthy: 9500
• Nick purchases a test that has 90% accuracy.
  • Sick Positive: 450
  • Sick Negative: 50
  • Healthy Positive: 950
  • Healthy Negative: 8550
• Nick feels fine, but the test results show positive. What's the probability he's actually healthy?

  • Positive Cases = 450 + 950 = 1400

  • Healthy Positive = 950

  • The probability of being healthy out of all positives = 950 / 1400 * 100 = 68%

    The probability of Nick to be healthy was calculated by dividing the amount of healthy positive (the desired outcome) to the sum of both healthy and sick positive cases (all outcomes).

    See: [[Estimating Probabilities#^Takeaway]]

    Probability Fundamentals - Briliant Course