Accidents Uniformity D9Dc82
1. **State the problem:** We are given the number of accidents in a city during a week and want to test if the accidents are uniformly distributed over the days of the week.
2. **Data given:**
| Day | Mon | Tues | Wed | Thu | Fri | Sat |
| No of accidents | 15 | 19 | 13 | 12 | 16 | 15 |
3. **Hypotheses:**
- Null hypothesis $H_0$: Accidents are uniformly distributed over the days.
- Alternative hypothesis $H_a$: Accidents are not uniformly distributed.
4. **Formula for chi-square goodness-of-fit test:**
$$\chi^2 = \sum \frac{(O_i - E_i)^2}{E_i}$$
where $O_i$ is observed frequency and $E_i$ is expected frequency.
5. **Calculate expected frequency:**
Total accidents = $15 + 19 + 13 + 12 + 16 + 15 = 90$
Number of days = 6
Expected frequency per day $E = \frac{90}{6} = 15$
6. **Calculate chi-square statistic:**
$$\chi^2 = \frac{(15-15)^2}{15} + \frac{(19-15)^2}{15} + \frac{(13-15)^2}{15} + \frac{(12-15)^2}{15} + \frac{(16-15)^2}{15} + \frac{(15-15)^2}{15}$$
$$= 0 + \frac{16}{15} + \frac{4}{15} + \frac{9}{15} + \frac{1}{15} + 0 = \frac{30}{15} = 2.0$$
7. **Degrees of freedom:**
$df = n - 1 = 6 - 1 = 5$
8. **Decision rule:**
At significance level $\alpha = 0.05$, the critical value from chi-square table for $df=5$ is approximately 11.07.
9. **Conclusion:**
Since calculated $\chi^2 = 2.0$ is less than critical value 11.07, we do not reject the null hypothesis.
**Final answer:** $\chi^2 = 1.998$ (rounded), Null Hypothesis not rejected.