Interpretation of confidence interval

Learning objectives

  • Interpret a confidence interval correctly.
    • You can claim to have the specified level of confidence that the interval you have computed actually covers the true value.
    • Understand the relationship of the sample size, n, to both the certainty (confidence level) and precision (margin of error).
    • For the same sample size and true population proportion, more certainty means less precision (wider interval) and more precision (narrower interval) implies less certainty.
  • Know and check the assumptions and conditions for finding and interpreting confidence intervals.
    • Independence Assumption or Randomization Condition
    • 10% Condition
    • Success/Failure Condition
  • Be able to invert the calculation of the margin of error to find the sample size required, given a proportion, a confidence level, and a desired margin of error.

Checklist