STATISTICAL TECHNIQUES AND TOOLS
CONFIDENCE INTERVALS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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z-distribution for mean cost
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t distribution for mean cost
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z-distribution for proportions
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t-distribution for proportions
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Detailed explanation-1: -The 95% confidence level is often used, though the 99% CI are used occasionally. At 99%, the width of the CI will be larger but it is more likely to contain the true population value, than the narrower 95% CI. Bioequivalence testing makes use of the 90% CI.
Detailed explanation-2: -For a population with unknown mean and known standard deviation, a confidence interval for the population mean, based on a simple random sample (SRS) of size n, is + z*, where z* is the upper (1-C)/2 critical value for the standard normal distribution.
Detailed explanation-3: -Strictly speaking a 95% confidence interval means that if we were to take 100 different samples and compute a 95% confidence interval for each sample, then approximately 95 of the 100 confidence intervals will contain the true mean value ().