Title: Confidence Intervals and the Normal Distribution | Statistical Analysis with Excel 2010: Using Excel with the Normal Distribution | InformIT
Headings: Statistical Analysis with Excel 2010: Using Excel with the Normal Distribution
Statistical Analysis with Excel 2010: Using Excel with the Normal Distribution
This chapter is from the book
Confidence Intervals and the Normal Distribution
The Meaning of a Confidence Interval
Constructing a Confidence Interval
Excel Worksheet Functions That Calculate Confidence Intervals
Using CONFIDENCE.NORM () and CONFIDENCE ()
Using CONFIDENCE.T ()
Using the Data Analysis Add-in for Confidence Intervals
Confidence Intervals and Hypothesis Testing
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Content: either the interval captures the mean or it doesn't. However, it is more rational to assume that the one confidence interval that you took is one of the 95% that capture the population mean than to assume it doesn't. So you would tend to believe, with 95% confidence, that the interval is one of those that captures the population mean. Although I've spoken of 95% confidence intervals in this section, you can also construct 90% or 99% confidence intervals, or any other degree of confidence that makes sense to you in a particular situation. You'll see next how your choices when you construct the interval affect the nature of the interval itself. It turns out that it smoothes the discussion if you're willing to suspend your disbelief a bit, and briefly: I'm going to ask you to imagine a situation in which you know what the standard deviation of a measure is in the population, but that you don't know its mean in the population. Those circumstances are a little odd but far from impossible. Constructing a Confidence Interval
A confidence interval on a mean, as described in the prior section, requires these building blocks: The mean itself
The standard deviation of the observations
The number of observations in the sample
The level of confidence you want to apply to the confidence interval
Starting with the level of confidence, suppose that you want to create a 95% confidence interval: