Major alternatives to the Classic Experimental Design

In summary, giving up any of the three defining features of the Classic Experimental Design has (at least) two important effects. Each concession creates a significant threat to our confidence that any improvements observed were actually attributable to the treatment we are studying. At the same time, each concession opens a door by enhancing, sometimes greatly, the feasibility of conducting work in settings that are the most true to everyday clinical practice. When the work is thoughtfully and responsibly conducted, the alternative designs can contribute to clinical knowledge in a way that is equally important to the contributions made by work that conforms to the stringent requirements of the "Classic" design. In the next article, we will discuss single-time-point designs, along with the important dictum, memorized by most everyone who has taken a course called "Introduction to Research" or "Introduction to Statistics" that correlation is not causation.     

Comments on “markovian processes with identifiable states: General considerations and applications to all-or-none learning”

When knowledge of the response sequence permits one to specify the sequence of theoretical states that occurred, we propose to say that the theory has observable states. Our earlier usage of identifiable conflicts with established usage in econometrics. We also present a revised definition of implication between theories that avoids a technical flaw in the earlier definition, and we correct a mistake in an example in our earlier paper.     

Counseling on the Information Highway: Future Possibilities and Potential Problems

The evolution of the Internet into the information highway offers many future possibilities and potential problems in the delivery of counseling services. Features of the current Internet are briefly reviewed, and the results of an analysis of counseling applications on the Internet are presented and discussed. Current experience with computer networks, counseling applications, and the likely features of the future information highway provides a foundation for exploring the potential benefits and limitations of using this technology in counseling.     

Invariance of inference time when information was presented in different linguistic formats

Ss read paragraphs varying in syntactic complexity, contiguity of information that was conceptually related, and amount of information relating to quantitative variables. Paragraphs were presented too briefly to allow full reading in many cases. In questions requiring use of the quantitative information, proportion of correct responses was influenced by syntax, contiguity, and number of variables from the paragraph. However, neither syntax nor contiguity influenced latency of correct answers, while number of variables, a factor affecting complexity of the process of answering, did influence correct response latency. The findings confirm and extend earlier results by Kintsch and Monk (1972) and give further support to the proposition that assimilation of information in linguistic input involves storing the semantic content of the message.     

An analysis of some conditions for representingN state Markov processes as general all or none models

Recently Markov learning models with two unidentifiable presolution success states, an error state, and an absorbing learned state, have been suggested to handle certain aspects of data better than the three state Markov models of the General All or None model type. In attempting to interpret psychologically, and evaluate statistically the adequacy of various classes of Markov models, a knowledge of the relationship between the classes of models would be helpful. This paper considers some aspects of the relationship between the class of General All or None models and the class of Stationary Absorbing Markov models withN error states, andM presolution success states.     

Introduction to the Technical Series: What is Science,and How Does It Help Us?*

Editor's Note: Readers trained in research have no need of a series of articles that introduce the value of the scientific method and the basic factors that comprise good research methodology. But readers who are primarily trained to do clinical work with families will find that today's healthcare environment increasingly requires that they be good consumers of research, as well as an increasing need for them to participate in studies of the models we wish to preserve. At a recent NIMH‐sponsored conference, a speaker lamented the probable demise of some of our more interesting family approaches because third‐party payers tend to support only evidence‐based interventions. Clearly, we need to be able to defend our practices, and understanding the value and essential components of scientific methodology and research studies is likely to become even more important in the future. This new series will attempt to provide an orientation for those of our readers who are interested. We welcome your response to these articles and your suggestions for future segments.     

Effect of meaningfulness on judgments of computability

The University of Michigan, Ann Arbor, Michigan 48104 After memorizing a set. of four equations, subjects were given problem frames specifying an unknown variable and two, three, or four given variables. The task on each item was to judge whether the presented variables corresponded to a problem that could be computed. (No values were given and no computation was carried out.) The main finding was a strong interaction: With formulas consisting of uninterpreted letters, judgments of uncomputable items were much slower than judgments of computable items; however, the difference between positive and negative items was much smaller when formulas consisted of meaningful concepts. Attempts to remove the interaction by presenting the nonsense formulas as an integrated network or by using a format allowing easy chunking of the variables in each formula did not succeed. At this point it appears most promising to investigate effects of meaningfulness on basic component processes, such as decisions about whether pairs of items come from the same formula.     

Equivalence classes of functions of finite Markov chains

A matrical representation of a Markov chain consists of the initial vector and transition matrix of the chain, along with matrices that specify which observable response occurs for each state. The likelihood function based on a Markov model can be stated in a general way using the components of the model's matrical representation. It follows directly from that statement that two models are equivalent in likelihood if they are related through matrix operations that constitute a change of basis of the matrical representation. Two necessary properties of a change matrix associating two Markov models that are members of the same equivalence class with respect to likelihood are derived. Examples are provided, involving use of the results in analyzing identifiability of Markov models, including a useful application of diagonalization that provides a connection between the problem of identifiability and the eigenvalue problem.