Travel Time Correlation Ddd730
1. **Problem Statement:**
Determine if there is a statistically significant relationship between students' travel time (in minutes) and their midterm exam scores at a 0.05 significance level.
2. **Statistical Method:**
We use the Pearson correlation coefficient $r$ to measure the strength and direction of the linear relationship between travel time and midterm scores.
3. **Hypotheses:**
- Null hypothesis $H_0$: There is no linear relationship between travel time and midterm scores, i.e., $\rho = 0$.
- Alternative hypothesis $H_a$: There is a linear relationship, i.e., $\rho \neq 0$.
4. **Formula for Pearson correlation coefficient:**
$$
r = \frac{n\sum xy - \sum x \sum y}{\sqrt{(n\sum x^2 - (\sum x)^2)(n\sum y^2 - (\sum y)^2)}}
$$
where $x$ is travel time, $y$ is midterm score, and $n$ is the number of paired observations.
5. **Calculate sums:**
- $n = 42$
- $\sum x = 1113$
- $\sum y = 1683$
- $\sum xy = 42201$
- $\sum x^2 = 51219$
- $\sum y^2 = 69225$
6. **Calculate numerator:**
$$
n\sum xy - \sum x \sum y = 42 \times 42201 - 1113 \times 1683 = 1772442 - 1873179 = -100737
$$
7. **Calculate denominator:**
$$
\sqrt{(42 \times 51219 - 1113^2)(42 \times 69225 - 1683^2)} = \sqrt{(2151118 - 1238769)(2907450 - 2833089)} = \sqrt{912349 \times 74361} \approx \sqrt{67851209589} \approx 260488.5
$$
8. **Calculate $r$:**
$$
r = \frac{-100737}{260488.5} \approx -0.3867
$$
9. **Test statistic for correlation:**
$$
t = r \sqrt{\frac{n-2}{1-r^2}} = -0.3867 \sqrt{\frac{40}{1 - (-0.3867)^2}} = -0.3867 \sqrt{\frac{40}{1 - 0.1495}} = -0.3867 \sqrt{\frac{40}{0.8505}} = -0.3867 \times 6.86 = -2.65
$$
10. **Degrees of freedom:** $df = n - 2 = 40$
11. **Critical value:** For $\alpha = 0.05$ two-tailed test and $df=40$, $t_{critical} \approx \pm 2.021$
12. **Decision:** Since $|t| = 2.65 > 2.021$, reject $H_0$.
13. **Interpretation:** There is a statistically significant negative linear relationship between travel time and midterm exam scores at the 0.05 significance level. This means as travel time increases, midterm scores tend to decrease.
14. **Possible factors:** Longer travel times may cause fatigue, reduce study time, or increase stress, negatively affecting academic performance. Other confounding variables may also influence this relationship.
**Final answer:** There is a significant negative correlation ($r \approx -0.39$) between travel time and midterm exam scores, indicating travel time affects academic performance negatively.