A-level of significance

TABLE 2-1 a. Levels of Significant Exposure to o-Crerol - Oral... 

Table II shows the result of the analysis. In this event only fission-product radionuclides were considered. As before, four nuclides are significant at well above the 99% confidence level all other nuclides have a level of significance at or below 30%. Since the estimated experimental errors are probably not realistic, a level of significance below 50% is probably not meaningful. Four nuclides are then necessary and sufficient.

The tR statistic has the Student distribution and is compared with the tabulated value of tam, at a level of significance a, where - is the number of control points and f-is the number of degrees of freedom for the replication variance. The null hypothesis that the equation is adequate is accepted if tRcontrol points. It should also be noted that Eq. (3.59) is valid for the same number of replications in each simplex point. The confidence interval for the response value is ... 

The National Coimcil for Radiation Protection (NCRP) has identified a negligible individual risk level (NIRL) as a level of annual excess risk of health effects attributable to irradiation below which further effort to reduce radiation to the individual is unwarranted. The NCRP emphasized that this level should not be confused with an acceptable risk level, a level of significance or a standard. The NCRP recommended a level around half the natural background radiation level the final recommended NIRL level is 1 mrem this level is now called negligible individual dose (NID) level (Harley, 2001, 2008). 

Looking up this value of t in a more complete table of t than the one in the Appendix, we find it corresponds to a level of significance of approximately 25%. That is to say, in the absence of any difference between the two foundries, if we repeatedly sampled from them we would get as large an apparent difference between them as we did here 1 out of every 4 times. The present result, therefore, is only a very slight indication of the possible superiority of Foundry B. 

To test the significance of each coefficient, we obtain the value of t as the ratio of the regression coefficient to its standard error, and look up this value of t with degrees of freedom equal to those of the residual variance. For ba.tir) for example, t = 0.7685143/0.2709 = 2.837 with 135 degrees of freedom. Reference to Table I in the Appendix shows that this corresponds to a level of significance of between 1% and 0.1%. 

What is the chance that an Increased risk of death will actually be detected After choosing a level of significance at which the null hypothesis (no increased risk) will be rejected (F. 05, say), the power of a comparison is the probability that, in fact, the number of deaths observed will be large enough to constitute a significant excess over the number expected If there were no Increased risk. 

If i is determined for various values of t during the coulometric procedure, a plot of log i versus t will yield a straight fine. The value of log io and i can be obtained from the intercept of the line with the log i axis at zero time, with the value of k being obtained from the fine slope -0.4343 k. This determination of i and k now permits the estimation of Qmax from equation (53). The amount of the reacting species can then be estimated from equation (47) without the time necessary to carry out the electrochemical reaction to quantitative completion. The values of i determined for various t values can be corrected for the residual current, if this latter has been shown by previous tests to reach a level of significance. 

No statistical significance and insignificance in this chapter refer to situations when anull hypothesis can be rejected at a level of significance >0.10. 

Neither study reported the dose of 1,1,2-trichloroethane applied, so neither was used as the basis for a level of significant exposure. 

Test rule The statistic M has approximately a distribution with — 1 degrees of freedom. This approximation is more appropriate for sample sizes larger than 3. If the observed value of M exceeds the critical value of the chi-square statistic for a level of significance a and k — 1 degrees of freedom, the hypothesis is rejected. 

The sign test to compare two treatments. We assume that there are several independent pairs of observations on the two treatments. The hypothesis to be tested states that each difference has a probability distribution having mean equal to zero. For each difference the algebraic sign is noted and then the number of times the less frequent sign is considered as the test statistic. There are speciahzed tables for the critical value of this quantity once a level of significance is chosen. 

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