This section further details two types of inferences on the slope parameter, considering both confidence intervals and hypothesis testing.

1. $0.743±0.578$

3. $−0.610±0.633$

5. $T=1.732$, $±t_{0.05}=±2.353$ , do not reject $H_0$

7. $0.6±0.451$

9. $T=−4.481$, $±t_{0.005}=±3.355$, reject $H_0$

11.  $4.8±1.7 words$

13. $T=2.843$, $±t_{0.05}=±1.860$, reject $H_0$

15.

1. $42.024±28.011$ thousand dollars,
2. $T=1.487$, $t_{0.05}=1.943$ , do not reject $H_0$;
3. $t_{0.10}=1.440$ , reject $H_0$

17. $T=4.096$, $±t_{0.05}=±1.771$, reject $H_0$

19. $T=25.524$, $±t_{0.0005}=±3.505$, reject $H_0$

21.
1. $2.550±0.127$ hundred psi,
2. $T=41.072$, $±t_{0.005}=±3.674$, reject $H_0$

23.
1. $(0.0014,0.0018)$
2. $H_0: β_1=0.001$ vs. $H_a: β_1 > 0.001$. Test Statistic: $Z=6.1625$. Rejection Region: $[1.28,+∞)$.

Decision: Reject $H_0$.

25.
1. $(101.789,131.4435)$
2. $H_0: β_1=90$ vs. $H_a: β_1 > 90$. Test Statistic: $T=3.5938$. $d.f.=58$. Rejection Region: $[1.296,+∞)$.

Decision: Reject $H_0$.