Statistical Terms
| Term | Definition | Example |
| Statistic | Summary of sample and estimation of unknown population parameter | NPV is estimated from sample |
| Parameter | Number summarizing population | NPV is determined for test in population |
| H0 | Specific statement about parameters of population | H0 is NPVPET/CT of less than 90% |
| HA | Broad statement that pairs with, yet is mutually exclusive from, H0 | HA is NPVPET/CT of at least 90% |
| Test statistic | Summary of information from sample | When comparing 2 means assuming normal distribution, with z as test statistic, z follows standard normal distribution |
| P value | Probability of obtaining sample statistic at least as extreme as test statistic in direction of HA if H0 were true | z of 2.26 (calculated from comparing 154 patients with observed FNR of 15% to 154 patients with observed FNR of 7%) corresponds to P value of 0.0238 |
| Type I error (α) | Probability of rejecting H0 when true | Phase 3 superiority trials are commonly designed with 1-sided type I error of 0.025 |
| Type II error (β) | Probability of failing to reject H0 when false (i.e., HA holds) | When clinical trials are designed, type II error is set priori, with β of 0.05–0.20 commonly used |
| Statistical power (1 − β) | Probability of rejecting H0 when HA is true | Clinical trials are commonly designed with 80%–95% power |
| CI | Range of possible values of true parameter based on specified level of confidence | Pathologic analysis of SLNs by routine hematoxylin and eosin revealed NPV of 0.94, with 95% CI of 0.88–0.98 (26). |
| Familywise error rate control | Control of probability of at least one type I error | Bonferroni adjustment divides type I error by number of tests |
| False-discovery rate control | Control of proportion of significant results that are actually false-positives | Hochberg step-down procedure orders P values to compare with adjusted α |
NPV = negative predictive value; NaF PET/CT = sodium fluoride positron emission tomography.