Answer:
c. Stdev
Step-by-step explanation:
Excel stdev function is not appropriate to construct confidence interval estimate, because the estimation of the proportion of defective items that are produced by a certain machine has binomial distribution.
stdev fuction is used for calculating standard deviations where sample has more than two different values. (multinomial)
Norm.s.inv function calculates inverse of the standard normal cumulative distribution, and countif counts the number of cells that meet a criterion. Both functions are used to construct confidence interval estimate
