Multiple comparisons tests

METH-induced changes in neuropeptide levels, selective Dj (SCH 23390) and D2 (sulpiride) dopaminergic receptor antagonists were coadministered. The results are expressed as percent of control to facilitate comparisons each value represents the mean SEM of five to seven animals. Data were subjeeted to either a Student s r-test (figures 4 and 5) or ANOVA analysis followed by a multiple comparisons test (figures 1, 2, and 3). Signifieanee was set at the. 05 level. 

Biologically meaningful and easier to resolve contrasts and multiple comparison tests. 

The distribution-free multiple comparison test should be used to compare three or more groups of nonparametric data. These groups are then analyzed two at a time for any significant differences (Hollander and Wolfe, 1973, pp. 124-129). The test can be used for data similar to those compared by the rank-sum test. We often employ this test for reproduction and mutagenicity studies (such as comparing survival rates of offspring of rats fed various amounts of test materials in the diet). 

One uses ANOVA when comparing differences between three or more means. For two samples, the one-way ANOVA is the equivalent of the two-sample (unpaired) t test. The basic assumptions are (a) within each sample, the values are independent and identically normally distributed (i. e., they have the same mean and variance) (b) samples are independent of each other (c) the different samples are all assumed to come from populations having the same variance, thereby allowing for a pooled estimate of the variance and (d) for a multiple comparisons test of the sample means to be meaningful, the populations are viewed as fixed, meaning that the populations in the experiment include all those of interest. 

Fig. 1. (—)-Iinalool attenuates mechanical allodynia induced by spinal nerve ligation in mice. (A and B) Mechanical allodynia developed and maintained over time following spinal nerve ligation (SNL). (A) A single dose of linalool (100 mg/kg s.c.) did not cause any significant changes compared to SNL and vehicle-treated animals. (B) Linalool administered daily for 7 days attenuated mechanical allodynia compared to SNL animals and SNL animals treated with the vehicle ( p < 0.001 vs vehicle ANOVA+Tukey test). Data are expressed as mean SEM of the value corresponding to 50% of pain threshold and are normalized to the basal value of each animal. Differences are evaluated using oneway analysis of variance (ANOVA), followed by post hoc Tukey multiple comparison tests, p < 0.05 was regarded as significant.

Fig. 1. BEO dose-dependently reduces infarct size after permanent MCAo. Representative images of brain sections from (A) rats in — 5) sacrificed 24 h after permanent occlusion of middle cerebral artery (24 h MCAo) and (B) BEO-treated rats (n — 5) prior to MCAo BEO (0.5 ml/kg) was administered i.p. 1 h before MCAo. Brain sections were stained by TTC the ischemic region appears as a pale-stained area whereas the viable tissue is stained red. (C) Effects of different doses of BEO (0.05—1 ml/kg), administered i.p. 1 h before MCAo, on infarct volume results are expressed as mean S.E.M. (n = 4-6 per group). and Denote P< 0.05 andP< 0.01 versus 24 h MCAo, respectively (ANOVA followed by Dunnett multiple comparisons test).

Table 7.1. Trellis for the Ibkey Multiple Comparison Test...

The statistical evaluation of weaving test data Indicated that the yarns treated with degraded starches performed as well as yarns treated with conventional hot size. The multiple comparison testing of the three population means Indicated that... 

Duration of action of the compounds is assessed by determining the period of time for which the inhibitory effects remain significantly different from vehicle controls. Statistical analysis of the data is performed by a repeated measure analysis of variance (ANOVA) followed by pairwise comparisons against control at each time period using Fisher s LSD multiple comparison test. 

One-way ANOVA showedp < 0.0001 for each endpoint. Bonferroni s multiple comparison test showed significant difference p < 0.001) compared to vehicle-injected control... 

FIGURE 42.8. Ipsilateral cerebral F2-IsoPs (A) and F4-Neu-roPs (B) concentrations following i.c.v. KA with or without vitamin E (Vit E) or V-tert-butyl-a-phenylnitrone (PBN) pretreatment. Brains from mice exposed to KA were collected 30 min post-injections (n > 5 for each group). One-way ANOVA had p < 0.0001 with Bonferroni s multiple comparison tests significant for KA vs control, Vit E + KA or PBN + KA treatment. 

The NOEC and the LOEC are the usual calculations reported from chronic toxicity tests. The NOEC is the highest concentration in which the measured effect is not statistically different from that of the control. The LOEC is the lowest concentration at which a statistically significant effect occurred. These concentrations are based on the most sensitive effect parameters, that is, hatchability, growth, and reproduction. The statistical procedure for these calculations combines the use of analysis of variance techniques and multiple comparison tests. In some cases, the maximum acceptable toxic concentration (MATC) is reported from chronic toxicity results. The MATC is a concentration [x) that is within the range of the NOEC and LOEC NOEC a < LOEC. The first-effect concentration can be expressed as the geometric mean of the two terms. 

Dunn s post test A statistical multiple comparison test used post hoc after certain other multiple group tests (e.g. Kruskal-U llis) to narrow down which groups are significantly different from which other groups, duodenal ulcer See peptic ulcer, duplicate genes Two identical genes that display the same phenotypic action, but occur on different chromosomes. 

Statistical treatments. The data were processed with the SAS statistical package version 6.11, 4 edition (SAS Institute, Inc., Cary, NC). ANOVA analyses were performed at level a = 0.05, according to the model attribute = product + subject + product x subject, with subject as a random effect. Means were compared with the Newman - Keuls multiple comparison test (Student t... 

Fig. 9. Efficiencies of conversion reactions between homologous and heterologous isoforms of PrP. Conversion efficiencies of [ S]-PrP-sen proteins in cell-free reactions with equivalent amounts of different PrP-res molecules. The results show the mean percentage of the input 24 27 kDa [ S]-PrP-sen converted to the 17-20 kDa PK- resistant [ S]-PrP bands. PrP9JD-M/M and PrP9JD v/V designate human PrP-res derived from the brains of CJD patients homozygous for methionine or valine at residue 129, respectively. Within the groups of values for each type of PrP-res, the statistical significance of the difference of the means relative to the maximum mean percent conversion of PrP-sen of the same species (boxed) was assessed with a one way ANOVA with Dunnett s multiple comparison test , p < 0.05 , p < 0.01. The norm mean column shows means within each PrP-res group normalized to the homologous conversion (boxed). Adapted from Raymond et al, 2000.

Figure 3. Samples evaluation results of the multiple comparison test (Significant leve1=9594).

For duration of response, males sat in the female stimulus area significantly more than the other two stimulus areas (Figure 3, W=7.283, n=53, P=0.026). Multiple comparison tests showed that the difference existed between female and male (P<0.05), but not between the other treatments. No significant differences were found in other behavioral patterns for male test subjects. There were no significant differences in the duration of any of the behaviors performed by females. 

Activity (Figure 4) was significantly different between treatments (Kruskal-Wallis 5, 216=19.85 / =0.001). A 2-tailed multiple comparisons test revealed that the activity response to the W/W treatment was significantly less than the response to NFo (/ =0.013) and Mx/Mx (F<0.001). There were no significant differences between any of the aged treatments Fo, F48, NFo, NF4s-... 

Figure 4. Activity levels shown as in Figure 2. Treatments are identical to Figure 3. Letters indicate significant differences for each treatment based on a Kruskal-Wallis and two-tailed multiple comparisons test.

Pairwise comparisons among 80 adult E. rufescens using a distribution-free multiple comparison test based upon the Kruskal-Wallis ranked sums test (Hollander Wolfe, 1973) indicate that the active surface area of paired males is significantly larger than that of single males and those of both paired and single females (P < 0.05 for each comparison)... 

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