Linear Relationship Test
1. **State the problem:** We want to test if there is evidence of a linear relationship between starting salary and GPA at the 0.01 significance level.
2. **Hypotheses:**
- Null hypothesis ($H_0$): There is no linear relationship between GPA and starting salary ($\rho = 0$).
- Alternative hypothesis ($H_a$): There is a linear relationship ($\rho \neq 0$).
3. **Formula and test:** We use the Pearson correlation coefficient $r$ to measure linear association and perform a hypothesis test using the test statistic:
$$ t = \frac{r\sqrt{n-2}}{\sqrt{1-r^2}} $$
where $n$ is the number of data points.
4. **Calculate $r$:** Using the data,
- GPA: $[2.3,3.9,3.2,3.5,3.8,2.5,3.3,3.9,2.2,2.8]$
- Salary: $[44.1,33.8,42.6,28.4,34.3,31.3,40.8,41.2,26.2,28.9]$
Calculate means:
$$ \bar{x} = 3.14, \quad \bar{y} = 35.16 $$
Calculate covariance and variances, then
$$ r \approx -0.58 $$
5. **Calculate test statistic:**
$$ n=10 $$
$$ t = \frac{-0.58 \times \sqrt{8}}{\sqrt{1-(-0.58)^2}} \approx -2.22 $$
6. **Determine critical value:** For $\alpha=0.01$ and $df=8$, two-tailed critical $t$ is approximately $\pm 3.355$.
7. **Decision:** Since $|t|=2.22 < 3.355$, we fail to reject $H_0$.
8. **Conclusion:** There is not sufficient evidence at the 0.01 level to conclude a linear relationship between GPA and starting salary.
**Final answer:** We fail to reject the null hypothesis. There is not, at the 0.01 level of significance, sufficient evidence of a linear relationship between starting salary and GPA.