Chi-squared test
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Chi-squared test
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A study was conducted at a large medical center to assess the association between rotavirus vaccine and the incidence of intussusception in pediatric patients. The patients were randomized into groups that either received the trial vaccine or a placebo injection. Data from the study is presented below. Which of the following analysis methods would be most appropriate to assess the statistical significance of these results?
| Intussusception within 6 months | No intussusception within 6 months | Total studied | |
| Vaccine administered | 421 | 671 | 1092 |
| Vaccine not administered | 263 | 524 | 787 |
| 784 | 1195 |
Summary
The chi-squared test is a statistical method used to test the independence of two categorical variables. The chi-squared statistic is calculated as the sum of the squared differences between the observed and expected frequencies for each category, divided by the number of degrees of freedom.