Median, statistical analysis

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). 

Fig. 6 Effect of methylphenidate on Acquisition of the PAR in juvenile rat pups. Juvenile rat pups (day 15-16) were tested for acquisition of a multi-trial PAR. Littermates were equally divided into vehide or drug treatment groups. Methylphenidate salt was given ip at a dose of 3 mg/kg (base), 30 mins prior to training. Animals were returned to their home cage with their littermates for the intertrial time period. indicates statistically significant differences between drug-treatment group and vehide-treatment group at the specific trial. Non-parametric statistical analysis (Kruskal-Wallis test) was conducted on median latencies (sec). Mean + SEM entry latendes (sec) are presented (n = 12-18/group).

A third measure of location is the mode, which is defined as that value of the measured variable for which there are the most observations. Mode is the most probable value of a discrete random variable, while for a continual random variable it is the random variable value where the probability density function reaches its maximum. Practically speaking, it is the value of the measured response, i.e. the property that is the most frequent in the sample. The mean is the most widely used, particularly in statistical analysis. The median is occasionally more appropriate than the mean as a measure of location. The mode is rarely used. For symmetrical distributions, such as the Normal distribution, the mentioned values are identical. 

Median lethal concentration of a test material in the test matrix (e.g., growth medium) that is calculated to exhibit a lethal effect to 50% of a group of test organisms during exposure over a specified period of time. The LC50 and its 95% confidence limits are usually derived by statistical analysis of mortalities in several test concentrations. The duration of exposure must be specified (e.g., 48-h LC50). Volume 1(1,4,10), Volume 2(5). 

The methods of robust statistics have recently been used for the quantitative description of series of measurements that comprise few data together with some outliers [DAVIES, 1988 RUTAN and CARR, 1988]. Advantages over classical outlier tests, such as those according to DIXON [SACHS, 1992] or GRUBBS [SCHEFFLER, 1986], occur pri-marly when outliers towards both the maximum and the minimum are found simultaneously. Such cases almost always occur in environmental analysis without being outliers in the classical sense which should be eliminated from the set of data. The foundations of robust statistics, particularly those of median statistics, are described in detail by TUKEY [1972], HUBER [1981], and HAMPEL et al. [1986] and in an overview also by DANZER [1989] only a brief presentation of the various computation steps shall be given here. 

Data from subjects who experience emesis during the course of a BE study for immediate-release products should be deleted from statistical analysis if vomiting occurs at or before two times median Tmax. In the case of modified-release products, the data from subjects who experience emesis any time during the labeled dosing interval should be deleted. 

The one thing at which Excel does not excel is statistical analysis. The (very basic) level of material covered in this chapter is about at (if not beyond) the limit of its capabilities. It can be used to generate means, medians, SDs and quartiles, but while the first three are OK, the quartile values generated are somewhat unconventional and will not be pursued further. The mean, median and SD of a data set can be generated by using either worksheet functions or the Data Analysis tool. 

NIR has been used to determine the mass median diameter of a micronized active compound contained in a lactose monohydrate at a concentration of 4% by weight and a size between 8 and 20 pm [223]. Multivariate statistical analysis was applied to zero order NIR spectra using particle size distributions by low angle laser light scattering as a reference technique. Due to its speed, simplicity and low operating costs it was demonstrated that this is a viable alternative to other methods used to carry out this type of analysis. 

Total range of xl measurements Total range of x2 measurements Total range of differences (x2 - xl) Test for normality of differences (Anderson-DarUng test) Statistical analysis of differences Median Mean SD... 

The data is then statistically summarized and the resulting report issued to subscribers. The report consists of the following All participants data normalized to 100% (Table 3), the statistical analysis of reported results (Table 4). The statistical summary includes the mean, median, estimate of standard deviation, estimate of standard error, number of observations and number of outliers. 

Empirical evidence indicates that the majority of the respondents locate their service quality score at the right-hand side of the scale (Brown et al. 1993 Parasuraman et al. 1988 1991 Peterson and Wilson 1992). This distribution is referred to as negatively skewed. A skewed distribution contains several serious implications for statistical analysis. To begin with, the mean might not be a suitable measure of central tendency. In a negatively skewed distribution, the mean is typictilly to the left of the median and the mode and thus excludes considerable information about the variable under study (Peterson and Wilson 1992). Skewness also attenuates the correlation between variables. Consequently, the true relationship between variables in terms of a correlation coefficient may be understated (Peterson and Wilson 1992). Einally, parametric tests (e.g., t-test, F-test) assume that the population is normally or at least symmetrically distributed. 

The river sediment in the project mainly comes from basins. According to the statistical analysis of Datong Station in the upper reaches during 1951-2011, the maximum sediment concentration is 3.24 kg/m, the minimum sediment concentration is 0.016 kg/m, and the mean sediment concentration is 0.428 kg/m. After the Three Georges Reservoir started to reserve water in 2003, the mean sediment runoff over the years has reduced from 0.14 billion tons before water reserving to 0.14 bilhon tons after water reserving. Before and after water reserving, the sediment concentration has reduced by about 50%. The bed load is fine sand, with 0.10-0.25 mm median particle diameter the median particle diameter of suspended sediment is about 0.01 nun. 

A total of 16,492 participants with type 2 diabetes or at risk for cardiovascular events were randomized to saxagliptin or placebo (on a background of standard of care for diabetes and cardiovascular risk factors) and followed for a median of 2.1 years. The primary endpoint was occurrence of MACE outcomes. A primary endpoint event occurred in 613 participants in the saxagliptin group and in 609 participants in the placebo group. The statistical analysis plan prespecified that a test for noninferiority would be conducted first, followed by a test for superiority. Saxagliptin did not increase or decrease the rate of MACE outcomes (hazard ratio=1.00, 95% CI=0.89-1.12 p<0.001 for noninfeiiority, p=0.99 for superiority). 

Median In statistical analysis, that value point which is precisely in the center (i.e., half the value points fall below the median and half lie above the median). 

Results can be printed or saved to disk or other medium, with the form and information produced limited only by the software in use. Typical information obtained can include Young s modulus, proof stress, yield point, area under curve, average load, load at a given deflection, deflection at a given load, secant modulus, median of peak heights, peak load after initial peak, flexure modulus, n value, k factor, true stress and true strain. Printing of standard test reports and statistical analysis are also possible. 

Manning et identified 273 polymer projects that had been instituted or planned as of 1983. According to a statistical analysis of the fieldwide projects, median recovery of oil was 2.91 % OOIP, or 4.02% of the remaining oil in place (OIP) at the start of the projects. This amounted to a median recovery of 24.9 STB/acre-ft and 2.34 STB oil recovered per 1 Ibm of polymer injected. Incremental oil recovery by polymer-augmented waterflooding is not large on a percentage basis. Nonetheless, the incremental recovery can be sufficient to yield a satisfactory economic return. 

---