In order to construct a 90% confidence interval for the population mean when the population standard deviation is unknown and the sample size is 18, you should use the t-value indicated as:
A) t0.10,18
B) t0.10,17
C) t0.05,18
D) t0.05,17
E) t0.90,17

Question

Quizplus · Accepted Answer

When the population standard deviation is unknown and the sample size is 18, the degrees of freedom for the t-distribution is 17 (n-1). For a 90% confidence interval, you need the t-value for the 5% significance level in each tail, which is t0.05,17.

In Order to Construct a 90% Confidence Interval for the Population