Biostatistics Tutorial Week 5

Which is NOT true about the confidence interval?

• Its upper limit is larger than the mean and its lower limit is smaller than the mean

• If drawn randomly, repeated samples are likely to produce the same estimates of CI

• When calculating the CI, we can find the the z-score from the standard normal distribution table

• The z-score to calculate the 90% CI for a population mean is 1.65

Which factor can make a confidence interval narrower?

• A larger population size

• A smaller population size

• A smaller sample size

• A lower level of confidence

Which is true about the confidence interval

• The 95% CI means that 95% of the population would have a value that falls into the interval.

• We don't need the standard error of the mean or standard deviation to calculate the CI

• It provides a range of values within which the sample mean is likely to fall

• The higher the level of confidence, the wider the CI

Which of the following factors does not affect the width of a confidence interval?

• Standard error of the mean

• Standard deviation

• Level of confidence

• Population size

We don’t know whether the confidence interval does or does not capture the true population parameter because it's impossible to obain the true population value. Therefore, the values within the interval, compared to those outside the interval, are equally compatible with the true value

• TRUE

• FALSE

• It depends on whether the distribution is normal or skewed.

Which statement is NOT true?

• Confidence interval is not the same with the reference range even when the distribution is normal

• The confidence interval tells us a range of plausible values for the population mean

• The reference range tells us a range for individual observations

• If I want to know my height is within the 95% of the population, I should use the 95% CI