Variables, intervening

Figure 5.26 (A) The two 90° pulses are applied with an intervening variable

A major problem, when trying to ascertain the long-term effects of a particular single experience, is that many intervening variables (e.g., use of dmgs or alcohol, trauma, illness) muddy the waters absolute certainty is therefore unattainable. 

In considering how the initial state of yo impacts yt, the distribution of yt given yo, denoted here as P (yJyo), needs to be examined, yt depends directly on yo because the intervening variables (yo, yi,..., yi-i) are not provided. P. yo) will eventually converge to a unique invariant (or stationary) distribution that is independent of yo or t as the chain gradually forgets its initial state, subject to regularity conditions. 

As with all research, manuscripts must undergo peer review. Many authors who submit research to chemical education research features or Journals are surprised when their manuscripts are critiqued for drawing conclusions unsupported by their data. Sometimes this is a result of not developing researchable questions or not selecting an appropriate methodology that controls for intervening variables. But in some cases, the critique centers on the construction of inappropriate conclusions based upon the data collected or analyzed. Cooper (Chapter 11) addresses this point and demonstrates how the use of a theoretical basis for an experiment can help interpret the significance of research results. 

When intervening variables are identified, they can also be analyzed through sub-questions. For instance, when investigating whether one approach is better overall than another, sub-questions could explore this effect for women vs. men, high math-achieving vs. low math-achieving students, or traditional vs. returning students. 

Beaver in their natural setting are almost ideal experimental mammals for bioassays in the field with all its ecological complexity. Consistent results were obtained despite numerous uncontrollable intervening variables and the fact that their largely nocturnal behavior precludes prolonged detailed observation. 

The treatment of uncertainties requires the use of probabilistic methods, estimating the probability of exceeding response targets for the different performance requirements, for example, on an annual basis. The dynamic structural responses are highly nonlinear, and their time history must be found by numerical (e.g., finite elements) analysis for the duration of the earthquake. In a thorough analysis, the nonlinearity of the response is further increased when the interactions between the structure and the foundations are included. It is not possible to establish an explicit relationship between the intervening variables and the dynamic responses, and results can only be obtained in a discrete manner, given specific values of the structural variables and a particular earthquake record. Reliability calculations depend on simulations... 

Figure 3 shows a generic reinforced concrete portal frame, for which the intervening variables considered, with their corresponding bounds, were number of stories NS = 3 to 10 number of bays NB = 1 to 4 bay span XL = 300 to 600 cm (all equal) mass per unit length for each story m = 2.15 x 10 to 4 x 10 KNs /cm characteristic concrete compressive strength = 20 to 40 MPa beam width bh = 15 to 30 cm ... 

In this second application, the objective is to obtain an optimum longitudinal steel reinforcement ratio in order to achieve a minimum steel weight. The design parameters are as shown in Table 6. The frame is the same as in Application 1, with the remaining intervening variables as per Table 2. 

Neural networks can be trained for the mean and for the standard deviation of a structural response over a set of ground motions. The input to the networks will then be the remaining random intervening variables. 

Prossin AR, Zalcman SS, Evans SJ, Mclnnis MG, EUingrod VL. A pilot study investigating tumor necrosis factor-a as a potential intervening variable of atypical antipsychotic-assodated metaboUc syndrome in bipolar disorder. Ther Drug Monit 2013 35(2) 194-2Q2. 

Intervening variables mediation between the independent and dependent variables. An intervening variable is one that - as its name implies - intervenes between the independent variables that we manipulate and die dependent variables that we measure. When 1 described the effects of uncertainty on reaction time, I also used die term expectancy. In fact, to understand the relationship we posit a psychological, unobservable term that we believe intervenes between the independent and dependent variables. We assume that the physical measure of uncertainty is related to the unobservable variable of expectancy. Expectancy, in turn, is assumed to directly affect the dependent variable. Thus, the vertical chain of independent intervening dependent variables in Figure 2-1 constitutes the basic relationships that are the focus of most experimental research. 

But simply replicating the results does not validate them. The issue of validity is most often involved when we assume intervening variables and rely on surrogate measures of safety (rather than crash involvement). Thus, we should always question the validity of findings that are based on research in driving simulators and in studies relying on drivers self-reports or responses to questionnaires. In neither instance do we measure actual driving behavior, and in neither case do we know how to consider the accidents relative to real ones. 

On-the-road performance is just one of many intervening variables that mediate between driver skills and limitations and crash involvement. Therefore, it should not be surprising that the relationship between acuity and crash involvement is conceptually more tenuous than between acuity and on-the road visual performance. Nearly all of the studies that attempted to relate visual acuity to crash involvement failed to find any practically significant relationships between the two (for reviews of the many past studies see Owsley and McGwin, 1999 Shinar, 1977 Shinar and Schieber, 1991 DfT, 2005). 

The value of time - an intervening variable in the effects of congestion on aggression... 

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