All::Clinical Science::Study Design::Confidence interval
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What is a confidence interval?
a range of estimates for an unknown parameter
Confidence intervalWhat does a 95% confidence level mean?
that the confidence interval should contain the true effect of intervention 95% of the time
Confidence intervalWhat is standard error of the mean?
a measure of the spread expected for the mean
a.k.a how 'accurate' the calculated sample mean is from the true population mean
Confidence intervalHow is standard error of the mean calculated?
- SEM = SD / square root (n)
- where SD = standard deviation and n = sample size
- therefore the SEM gets smaller as the sample size (n) increases
How would you calculate a 95% confidence interval?
- lower limit = mean - (1.96 * SEM)
- upper limit = mean + (1.96 * SEM)