Significance Test
| T Test | ||
| User Input | Values | |
| null value | 8.2 | |
| alpha | 0.05 | |
| Summary Statistics | ||
| Sample Mean | 7.822312925 | |
| Standard Deviation | 0.704268864 | |
| Sample Size | 294 | |
| Calculations | ||
| Standard Error | 0.041073794 | |
| Test Statistic | -9.195329576 | |
| Degree of Freedom | 293 | |
| Alternative Hyposthesis Ha: mu>mu_0 | ||
| p-value - p_upper | 0.025000082 | |
| Decision | Reject Ho | |
According to a 2001 study conducted by the Department of Water – City of Chicago, “the average pH in the Chicago district waters is at 8.20.” I performed a significance test to determine if the population pH value in 1997 was higher than the 2001 average level. The null hypothesis is that there is no significant difference between the pH in 1997 versus the pH in 2001. The alternative hypothesis is that the population pH value in 1997 was higher than the 2001 average level. The calculated p value came out as 0.025. This value is smaller than the value of alpha, thus the null hypothesis can be rejected. In other words, there is a significant difference between the pH in 1997 and the pH in 2001. However, the alternative hypothesis is not necessarily confirmed, in fact it must be rejected.