Final answer:
To find the values of t for given probabilities and degrees of freedom, we use the table of critical values of the t-distribution.
Step-by-step explanation:
(a) To find t0.025 when v=10, we need to refer to the table of critical values of the t-distribution. Since we are looking for a two-tailed test and a confidence interval of 95%, we can find the value in the table. The table indicates that t0.025 for 10 degrees of freedom is approximately 2.228.
(b) To find t0.005 when v=19, we use the same process. The table shows that t0.005 for 19 degrees of freedom is approximately 2.861.
(c) To find t0.90 when v=7, we refer to the table once again. We find that t0.90 for 7 degrees of freedom is approximately 1.895.