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A population is known to have a population standard deviation o=4.A sample of size n=64 is drawn.The sample mean is 21.4 and sample standard deviation is 4.1. The lower limit of the 95%confidence interval is

Question

A population is known to have a population standard deviation o=4.A sample of size n=64 is drawn.The sample mean is 21.4 and sample standard deviation is 4.1. The lower limit of the 95%confidence interval is

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Solution

To calculate the lower limit of the 95% confidence interval, we first need to find the standard error of the mean. The standard error (SE) is calculated as the standard deviation (σ) divided by the square root of the sample size (n).

Given: σ = 4 (population standard deviation) n = 64 (sample size)

SE = σ / sqrt(n) = 4 / sqrt(64) = 4 / 8 = 0.5

Next, we need to find the z-score that corresponds to the 95% confidence level. The z-score for a 95% confidence interval is approximately 1.96 (you can find this value in a standard z-table).

Finally, we calculate the lower limit of the confidence interval using the formula:

Lower limit = sample mean - (z-score * SE)

Given: sample mean = 21.4 z-score = 1.96 SE = 0.5

Lower limit = 21.4 - (1.96 * 0.5) = 21.4 - 0.98 = 20.42

So, the lower limit of the 95% confidence interval is 20.42.

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