Title: Confidence intervals for the Scottish Health Survey - gov.scot
Headings: Confidence intervals for the Scottish Health Survey
Confidence intervals for the Scottish Health Survey
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What is a confidence interval?
Why do we need confidence intervals?
What is a confidence level?
Can we reduce the width of our confidence interval to increase precision ?
What impact does sample size have on confidence intervals?
When should confidence intervals be used?
How to use confidence intervals to estimate change
How does a complex survey design affect confidence intervals?
How to report confidence intervals?
How to present confidence intervals in Excel
Useful links:
Representing confidence intervals in Excel
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Content: For the same estimate this range increases to (+/-3.7%) at the 99% level. Clearly a smaller range about our estimate (ie the margin of error) is more useful, when making inferences about our population. Can we reduce the width of our confidence interval to increase precision ? If our confidence interval is too large (ie the margin of error is large), then there are a number of methods we can use to reduce it, thereby improving the precision of our results. For example, we could increase our sample size (if possible), use a lower level of confidence (eg. change from 99% to 95%) or reduce the standard deviation. See below for more details on sample size and confidence intervals. What impact does sample size have on confidence intervals? It is important to recognise that it is our sample size that influences the margin of error (ie the confidence interval). The true size of the population does not affect it.