STD ERROR q1 N*

[Roxanita]

Serum LDL-cholesterol concentrations are measured in blood samples collected from 100 healthy volunteers. The data follow a normal distribution. The mean and standard deviation for this group is 130 mg/dL and 20 mg/dL, respectively. The standard error of the mean is 5.0. The 95% confidence interval about the mean is 120 to 140 mg/dL.
If blood samples are collected from 25 healthy volunteers instead of 100, which of the following best expresses the expected impact on the standard error and the 95% confidence interval about the mean?


Standard Error / Width of 95% confidence interval

A) ↓ ↓


B) ↓ ↑


C) ↓ no change


D) ↑ ↓


E) ↑ ↑


F) ↑ no change


G) No change ; ↓


H) No change ; ↑


I) No change ; no change

[Asclepius1]

Standard Error will increase because with fewer subjects one or two skewed results could send the standard deviation way up or down. The width of 95% confidence interval have to increase also because you are less confidence.