Stats reviewer

    Cards (20)

    • Estimate
      is the value of range of value, that approximates the population value
    • Point Estimate
      Is a specific numerical value of a population parameter. The sample mean X is the best estimate of a population mean
    • Interval estimate
      Also called as confidence interval, is a range of values used to estimate a parameter.
    • Confidence level
      Is the probability that the interval estimate will contain the trues population parameter.
    • Critical value
      Also known as confidence coefficient, are the z-values that is used in describing the characteristics of a target population. When (PSD) is known, z-values are used.
    • 90% confidence
      z = ±1.65
    • 95% confidence
      z = ±1.96
    • 99% confidence
      z=±2.58
    • formula
      Margin of error formula
    • Interval estimate is expressed as
      Lower limit (X-E<mean<X+E) Upper Limit
    • Degrees of freedom (df)
      are the numbers of values that are free to vary after a sample statistics has been computed.
    • Degrees of freedom formula
      df=n-1
    • Margin of error formula when PSD are unknown
      E=t(s/√n)
    • Interval estimate expression when sd is unknown
      (X-E˂µ˂X+E)
    • T distribution
      Is a probability distribution that is used to estimate population parameters when the sample size is small and/or the population variance is unknown.
    • T distribution
      Was developed by William Sealy Gosset in 1908
    • Formula of t distribution
       t=t=¯xμ/s/n¯x−μ/s/√n
    • When will we use the formula of t distribution?
      When n<30 and the population standard deviation is unknown
    • Properties of t distribution
      • Is symmetrical about 0
      • Is bell shaped like normal distribution but with heavier tails
      • The mean, median, and mode is equal to 0
      • The variance is always greater to 1. It is equal to v/v-2 where v is the number of degree of freedom
      • As the df increase, the curve looks more and more like the normal distribution
      • The standard deviation of t distribution varies with the sample size
      • The total area under at t distribution curve is 1 or 100%
    • Formula of variance
      V/v-2
      Where v is df
    See similar decks