Confidence Level Calculator

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Confidence Interval in Statistics is the measure of how certain we are with a result of a whole population for

an experiment or analysis. Confidence interval depends on few factors such as sample variation and sample

size and Confidence Interval calculator is an easy tool helpful to find this value.



Example 1: Given sample size in a given population is 15. If the standard deviation is 12 and the

sample mean is 18, find the 99% confidence interval for the given mean number.



In order to find the confidence interval (μ), we can use the formula:

x - tα/2(σ/√n) < μ < x + tα/2(σ/√n)

where x = Sample mean = 18

σ = standard deviation = 12

n = sample size = 15

tα/2 = 2.9768 (from the t – alpha values table)

18 – (2.9768 * 12/√15) < μ <18 – (2.9768 * 12/√15)

8.777 < μ < 27.22



Example 2: Given sample size in a given population is 10. If the standard deviation is 25 and the

sample mean is 40, find the 99% confidence interval for the given mean number.



In order to find the confidence interval (μ), we can use the formula:

x - tα/2(σ/√n) < μ < x + tα/2(σ/√n)

where x = Sample mean = 40

σ = standard deviation = 25

n = sample size = 10

tα/2 = 3.2498 (from the t – alpha values table)

40 – (3.2498* 25/√10) < μ <40 – (3.2498 * 25/√10)

14.31<μ< 65.69

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