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Confidence Intervals for Population Proportion - Excel definitions

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  • Confidence Interval

    Range of values estimated to contain the true population proportion with a specified level of certainty.
  • Population Proportion

    Fraction of individuals in a population exhibiting a particular characteristic, estimated using sample data.
  • Sample Proportion

    Ratio of favorable outcomes to total sample size, calculated from collected data.
  • Margin of Error

    Amount added and subtracted from the sample proportion to create the confidence interval boundaries.
  • Critical Value

    Number from the standard normal distribution used to determine the margin of error for a given confidence level.
  • Standard Normal Distribution

    Probability distribution with mean zero and standard deviation one, used for z-value calculations.
  • Alpha

    Probability of error, found by subtracting the confidence level from one; used in critical value calculations.
  • Confidence Level

    Probability that the calculated interval contains the true population proportion, often expressed as a percentage.
  • COUNTIF

    Excel function that counts occurrences of a specified value within a selected range of cells.
  • NORM.S.INV

    Excel function returning the z-value for a given left-tail probability in the standard normal distribution.
  • Lower Bound

    Smallest value in the confidence interval, calculated by subtracting the margin of error from the sample proportion.
  • Upper Bound

    Largest value in the confidence interval, calculated by adding the margin of error to the sample proportion.
  • Sample Size

    Total number of individuals surveyed or observed in the sample, used in proportion calculations.
  • Square Root

    Mathematical operation used in the margin of error formula to account for variability in sample proportions.
  • Random Selection

    Method of choosing individuals for a sample to ensure unbiased representation of the population.