A researcher is planning to construct a one-sample z ‑confidence interval for a population mean . Select the statements that would lead to a smaller margin of error, assuming the other factors remain the same.
A) The population standard deviation turns out to be higher than expected. B) The researcher increases the sample size. C) The researcher lowers the confidence level. D) The researcher decreases the sample size. E) The population standard deviation turns out to be lower than expected. F) The researcher raises the confidence level.

Step-by-step explanation:

Given that a researcher is planning to construct a one-sample z ‑confidence interval for a population mean

The confidence interval would be calculated as

Here margin of error = Z critical * std error determines the size of the confidence interval

Margin of error dependds on i) Z critical value ii) std deviation

iii) Inversely to square root of sample size.

Hence margin of error would be small if

.B) The researcher increases the sample size

C) The researcher lowers the confidence level

E) The population standard deviation turns out to be lower than expected.

both equations and proportions are better.

there is no grid

step-by-step explanation: