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

Pearson correlation coefficient

Chi-squared test

Foundational SciencesBiostatistics, epidemiology, population health, and interpretation of the medical literatureStudy interpretation and drawing conclusions from dataChance

USMLE® Step 1 ReviewBiostatistics, epidemiology, population health, and interpretation of the medical literatureStudy interpretation and drawing conclusions from dataChance

USMLE® Step 2 ReviewBiostatistics, epidemiology, population health, and interpretation of the medical literatureBack to the Basic SciencesStudy interpretation and drawing conclusions from dataChance

Definitions & Key takeaways

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.

Chi-squared test

Definitions & Key takeaways

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