Acharacteristic of all confidence intervals is that: a. a confidence interval always includes the population parameter. b. a confidence interval always increases in width as the sample size is increased. c. a confidence interval cannot include a value of 0. d. a confidence interval always increases in width as the level of confidence increases.

B. a confidence interval always increases in width as the sample size is increased.

Explanation:

Confidence interval is a statistical term used to describe a population growth parameter, which is unknown to the researcher. This interval represents a situation that can be calculated and that can present itself in different ways between one sample and the other, in relation to the existence of observable factors or not, proving to be reliable or not.

In summary, we can say that for this interval to be considered efficient, it is necessary that it always increase in width as the level of confidence increases.