Type 1 and Type 2 errors

• Type 1 error


  false positive

  e.g. p<0.10

  e.g. telling a man he's pregnant

  happens when significance level is too lenient

  optimistic error

  accept the alternative hypothesis when shouldn't

  reject the null hypothesis when shouldn't
• Type 2 error


  false negative

  p<0.01

  e.g. telling a pregnant women she's not pregnant

  happens when significance level is too stringent

  pessimistic error

  accept the null hypothesis when shouldn't

  reject the alternative hypothesis when shouldn't