7 ms·

70% is 20% better than random, don't buy that crib yet.

• dredmorbius 7y ago
  Might invest in a bushel basket.
• nostrademons 7y ago
  Would need to know how the sample was chosen for that test. If you sample women of reproductive age at random, there's decidedly not a 50/50 chance that she's actually pregnant: by rough estimation it should be about (1.75 [fertility rate] * 9 months [duration of pregnancy] / 30 years [reproductive lifespan] = 4-5%). If you give all of those woman a wheat/barley test and 70% of the positive tests were truly pregnant (implying about 6.25% test positives) that's actually pretty good, roughly 8x better than a coin flip. If you take a sample that's known to be half pregnant and half not pregnant and only 70% of the pregnant women are identified, it's decidedly less good.
• X6S1x6Okd1st 7y ago
  Depends on the true distribution of the classes. Although the naive strategy gets even higher accuracy if the classes are unbalanced.
• Drdrdrq 7y ago
  So, 100% is 50% better than random? Weird math.
• YokoZar 7y ago
  Sure it's better than flipping a coin, but how does it compare with just making an educated guess? For some demographics you might get a 70% success rate with something as stupid as "Have you been trying to get pregnant for a few months? If so assume you are."