Identify the critical t. An independent random sample is selected from an approximately normal population with unknown standard deviation. Find the degrees of freedom and the critical t-value (t?) for the given sample size and confidence level.
(a) n = 6, CL = 90%
(b) n = 21, CL = 98%
(c) n = 29, CL = 95%
(d) n = 12, CL = 99%
t-distribution. The figure on the right shows three unimodal and symmetric curves: the standard normal (z) distribution, the t-distribution with 5 degrees of freedom, and the t-distribution with 1 degree of freedom. Determine which is which, and explain your reasoning.
−4 −2 0 2 4
solid dashed dotted