Statistical significance transformations

As with all of our Fourier transforms of real data, we test the statistical significance of the periods so revealed by generating appropriate sets of Markovian data, each datum consisting of a constant, a, plus a random number e., where the random number e. 

Statistical Analysis. Analysis of variance (ANOVA) of toxicity data was conducted using SAS/STAT software (version 8.2 SAS Institute, Cary, NC). All toxicity data were transformed (square root, log, or rank) before ANOVA. Comparisons among multiple treatment means were made by Fisher s LSD procedure, and differences between individual treatments and controls were determined by one-tailed Dunnett s or Wilcoxon tests. Statements of statistical significance refer to a probability of type 1 error of 5% or less (p s 0.05). Median lethal concentrations (LCjq) were determined by the Trimmed Spearman-Karber method using TOXSTAT software (version 3.5 Lincoln Software Associates, Bisbee, AZ). 

While thep-value allows us the ability to judge statistical significance, the clinical relevance of the finding is difficult to evaluate from the calculated confidence interval because this is now on the log scale. It is usual to back-transform the lower and upper confidence limits, together with the difference in the means on the log scale, to give us something on the original data scale which is more readily interpretable. The back-transform for the log transformation is the anti-log. 

The responses Y2, Y5 and Y6 were transformed into natural logarithms to homogenize the distribution of the residues. Then, the F test was used to determine the statistical significance of the effects. An effect was considered as significant when F>4(4-F0.95(l,60). 

Fig. 2. Relationship between body temperature and hemorrhagic Transformation. Patients were divided into three groups according to the average value of body temperature during the first 3 d after admission. The difference in frequency among the groups was statistically significant by %2 tests with p < 0.05.

An exploratory analysis was performed using a four-factor ANOVA model, with treatment, period, and sequence as fixed factors and subject within sequence as random factor. The results from the ANOVA were used to calculate the back-transformed 90 % confidence intervals (Cl) for the differences between the fed and fasted condition in the log-transformed exposure measurements (Cmax, AUCo-t and AUCo-cc). For Cmax the difference between fasting and fed conditions was found to be statistically significant while this was not the case for the AUC parameters. 

Carcinogenic metal compoimds such as crystalline Ni3S2 induced a dose-dependent statistically significant incidence of transformation in secondary cultures of Syrian hamster cells. A chemically related compound, amorphous NiS, which is not carcinogenic, resulted in no statistically significant incidences of transformed colonies. Untreated control cultures also had no statistically significant incidence of transformation. We have... 

The assay system described in the present study should be useful in screening potential metal carcinogens for their ability to induce transformation. However, further work is required to demonstrate and validate that each of the various metals induce neoplastic transformation in tissue culture. A statistically significant number of transformed colonies induced by exposure of cells to each of the metal compounds must be cloned and derived into cell lines. The tumorigenic potency of these various cell lines must be tested in nude mice. 

Of 55 transformer workers who were exposed to Askarel PCBs (0.00001-0.012 mg/m ) for a mean duration of 3.75 years, 2 gave a history of removal of a melanoma (type not reported) (Emmett et al. 1988a). No melanomas were reported by 56 age-matched nonexposed subjects, and the difference between the groups was not statistically significant. 

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