Discovering confidence intervals
Confidence intervals are used in different ways depending on the field, but the basic idea is the same. A confidence interval is a range including the mean of your sample. We see what this looks like in Figure 8.3:
Figure 8.3 – Confidence interval
What does this interval actually mean? Some say that you are confident that the mean of the population, or “true mean,” will fall within this range, some say that you are confident that if you repeat the study, the new mean will fall within this range, and others say that you are confident that the actual value of an estimate will fall within this range. This is a heated and completely pointless debate; they effectively say the same thing. That said, for the purpose of this exam, we will assume the first definition is correct: you are confident the “true mean” falls within the interval.
How confident you are is really defined by the confidence...
