(a) For a t-distribution with 12 degrees of freedom,
. (b) In a t-distribution with 28 degrees of freedom,
for
.
(a) Using a t-table or calculator, find
for a t-distribution with 12 degrees of freedom. The value is approximately 0.145.
![\[ P(t \leq -1.14) \approx 0.145 \]](https://img.qammunity.org/2024/formulas/mathematics/college/okzc9p0nnqnfmtvanbod3kwvfpgwoqb44g.png)
(b) To find c such that
for a t-distribution with 28 degrees of freedom, we need to find the critical value. Since the t-distribution is symmetric, we can find the c value by finding
(half of 0.99). Using a t-table or calculator, the critical value is approximately 2.048.
![\[ C \approx 2.048 \]](https://img.qammunity.org/2024/formulas/mathematics/college/nuswp0j9dmkjstkpcsspad06uh5m2rq35z.png)