Means statistical significance

Conventionally a p (probability) value of < 0.05 is taken to mean statistical significance. This means that if p = 0.05 then the observed difference could occur by chance on 1 in 20 (5%) of occasions. In effect, this means a 5% chance of a false-positive result. 

This means statistically significant. To be of chemical significance, a component must also be statistically significant The reverse is not always true. There can be statistically significant differences, which are uninteresting from a chemical point of view. Aldehydes and ketones, for instance, are significantly different to each other in many respects, but in their reaction with lithium aluminum hydride they do not show any pronounced chemoselectivity. 

Alexandrov, N. N. and N. Go, Biological meaning, statistical significance, and classification of local spatial similarities in nonhomologous proteins. Protein Sci, 1994. 3(6) p. 866-75. 

It seems that the blue airplanes fly further than the white airplanes. There are statistical tests that can be used to determine whether the blue airplane results differ from the white airplane results in a significant way. Note that in this context, the term significant means statistically significant and is not the same as important. For example, a change in a polymer process may result in a statistically significant difference in polymer tensile elongation. 

Computer simulation is an experimental science to the extent that calculated dynamic properties are subject to systematic and statistical errors. Sources of systematic error consist of size dependence, poor equilibration, non-bond interaction cutoff, etc. These should, of course, be estimated and eliminated where possible. It is also essential to obtain an estimate of the statistical significance of the results. Simulation averages are taken over runs of finite length, and this is the main cause of statistical imprecision in the mean values so obtained. 

Male and female rats exposed to 2.5 mg/kg/day methyl parathion in the diet for 2 years had statistically significant reduced body weights when compared to vehicle controls (Suba 1984). This effect was not consistent throughout the study and did not occur in rats exposed to either 0.025 or 0.25 mg/kg/day methyl parathion. Mean food consumption values were significantly elevated in male rats but only within the first 13 weeks of the 2-year exposure to 2.5 mg/kg/day methyl parathion (Suba 1984). Females exposed to 2.5 mg/kg/day methyl parathion had significantly reduced food intake values during the first 2 weeks of exposure, but intake was significantly elevated from week 3 to termination. Effects on food... 

The significance level relates to the risk of designating a chance occurrence as statistically significant. Usually a 5% level is utilized for testing treatment effects. If a p-value of 0.04 is reported for a treatment effect, this means that there is only a 4% chance that the difference in response between the active and control treatments occurred due to chance. Keep in mind, however, that if many tests are run in a trial, it is entirely possible that one or two might be significant due to chance. As an extreme example, consider a study in which 100 statistical tests are run. We would expect five of those tests to show significance with a p-value of 0.05 or less due to chance. Therefore, it is essential to specify the main tests to be run in the protocol. Any tests that are conducted after the trial has been completed should be clearly labeled as post hoc exploratory analyses. 

Scale bar 200 pm. Red arrows indicate the avascular zones. Quantification of digital analysis of the fluorescence angiography images number of branching points (mm2) (B) and mean mesh size (102 pm2) (C) as markers of vessel density for CAM. P < 0.05 was considered to be statistically significant. Error bars represent standard error of the mean. 

Statistical analysis. Values are given as the mean SEM. Data are represented as averages of independent experiments, performed in duplicate or triplicate. Statistical analyses were done using the Student s t-test. P < 0.05 was considered statistically significant. 

RI = radiation intensity RH = relative humidity RT = relative temperature SH = soil moisture ST = soil temperature. Mean and range for each variable. Means followed by different letters (a, b) within the same column indicate statistically significant differences (P <0.05). 

High radiation intensity (RI) values are recorded at the edge (around 800 W/cm2 on average) and almost constant values under cover (forest interior), which mean, almost, only up to 2% of that value. The differences were statistically significant (H = 16.19 p < 0.01). 

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