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Confidence Intervals for Population Means - Excel definitions

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  • Confidence Interval
    A range of values, calculated from sample data, that likely contains the true population mean with a specified level of certainty.
  • Population Mean
    The average value of a variable for all members of a group being studied, often estimated using sample data.
  • Sample Mean
    The arithmetic average of observed values in a sample, used as an estimate of the population mean.
  • Margin of Error
    The amount added to and subtracted from the sample mean to create the bounds of a confidence interval.
  • Alpha
    The probability of error, found by subtracting the confidence level from one; determines the area in the tails of the distribution.
  • Confidence Level
    The probability, expressed as a percentage, that the confidence interval contains the true population mean.
  • Population Standard Deviation
    A measure of variability for an entire population, often denoted by sigma, used when known in calculations.
  • Sample Standard Deviation
    A measure of variability within a sample, denoted as s, used when the population standard deviation is unknown.
  • Normal Distribution
    A symmetric, bell-shaped distribution used when the population standard deviation is known for confidence interval calculations.
  • t-Distribution
    A probability distribution used instead of the normal distribution when the population standard deviation is unknown.
  • CONFIDENCE.NORM Function
    An Excel function that calculates the margin of error for a confidence interval using the normal distribution.
  • CONFIDENCE.T Function
    An Excel function that calculates the margin of error for a confidence interval using the t-distribution.
  • Lower Bound
    The value at the bottom end of a confidence interval, found by subtracting the margin of error from the sample mean.
  • Upper Bound
    The value at the top end of a confidence interval, found by adding the margin of error to the sample mean.
  • Sample Size
    The number of observations in a sample, denoted as n, which affects the width of the confidence interval.