
A Confidence Interval, A Brief Introduction

 A confidence interval is a range of numbers, used to describe a statistical parameter
and how sure the statistician is about its value.

 This interval might be represented in words, as in:
 The average is between 25 and 45.

 This interval might be represented in symbols, as in:
 25 < µ < 45.

 This interval might be represented on a number line, as in:


 It might be used in conjunction with the area under a normal curve,
as in: "within 2 standard deviations of the mean."


 It might be used when reporting the error in a survey,
as in: "65% supported the proposition, with a 4% margin of error."


 It might be used when completing a twotailed hypothesis test,
as in: "The average is 0. With 95% confidence, test the alternate hypothesis that the average in not 0."


 In each case the confidence interval is a range of scores.
