Slovin's Formula & Cochran's Formula

• Slovin's Formula:

  • n refers sample size
  • N refers population
  • e refers margin of error

  
• Margin of Error

  • percentage points your results will differ from the real population value
  • higher or lower of level of confidence
  • 95% confidence level yields a margin of error of 5% or ±5% (plus or minus 5 percent)
  • The acceptable margin of error usually falls between 4% and 8% at the 95% confidence level
  • no margin of error - 5 % - assumed e
• Cochran's Formula - large populations

  p - estimated proportion of the attribute present in population

  q - 1-p

  e - desired level of precision (margin of error)

  If there's no p - input 0.5 in p

  
• Level of Confidence and z