When constructing a Confidence Interval for the population mean and both the sample standard deviation and the population standard deviation are known, which of the following should be used?

(A) normal distribution using the sample standard deviation
(B) normal distribution using the population standard deviation
(C) student-t distribution using the population standard deviation
(D) student-t distributuion using the sample standard deviation

Arandomized controlled trial is designed to evaluate the effect of metoprolol in patients with heart failure. while preparing for statistical analysis, the researcher reviews some common types of statistical errors. which of the following statements is true regarding a type i error in a clinical study? a. the study is not significantly powered to detect a true difference between study groups. bthe null hypothesis is true but is rejected in error. c. the null hypothesis is false but is accepted in error. d. type i error is also known as beta and is usually 0.1 or 0.2. e. type i error depends on the study's confidence interval.