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1. width of confidence interval increases when confidence level changes from 95% to 99% and
width of confidence interval decreases when confidence level changes from 95% to 80%.
2. We take a sample of 80 students, who got a mean score of 78 in exam. If it is known that
population standard deviation is 8. We can find confidence interval for given three confidence
levels.
We know, lower confidence limit for confidence interval for the mean with the population
standard deviation known is given by:
𝑥̅ − 𝑧𝛼/2 ∗

𝜎
√𝑛

Whereas, upper confidence limit for confidence interval for the mean with the population
standard deviation known is given by:
𝑥̅ + 𝑧𝛼/2 ∗

𝜎
√𝑛

With change in confidence level from 95% to 99% or to 80%, the value of 𝑧𝛼/2 changes, which
leads to change in lower and upper confidence limits, so confidence interval c...