Filosofía de la matemática

La filosofía de las matemáticas es una rama de la filosofía. Según Michael Dummett puede considerarse que hay cuatro preguntas fundamentales sobre el contenido de la filosofía de las matemáticas:

1. ¿Cómo sabemos que nuestras teorías matemáticas son verdaderas?
2. ¿Sobre qué son las matemáticas? En otras palabras, si un enunciado matemático es verdadero, ¿qué lo hace verdadero? ¿En virtud de qué es verdadero?
3. ¿Las verdades matemáticas son verdaderas por necesidad? Y, si lo son, ¿cuál es la fuente de esta necesidad?
4. ¿Cómo es posible aplicar las verdades matemáticas a la realidad externa? Y ¿en qué consiste esta aplicación? (Dummett, 1998, p. 124). También se plantean otras cuestiones como: ¿Qué significado tiene referirse a un objeto matemático? ¿Cuál es la naturaleza de una proposición en matemáticas? ¿Qué relación hay entre lógicay matemática? ¿Cómo se explica la belleza de las matemáticas?

Tipos de muestra

http://www.monografias.com/trabajos42/seleccion-muestra/seleccion-muestra2.shtml

1. Tipos de muestra

Hay varios criterios para clasificar las muestras, pero se adoptará el criterio que emite Freud (1977), Rivas (1991), Moráguez (2005), entre otros, por ser uno de los más difundidos y empleados en la actualidad.

Las muestras se agrupan en dos grandes dimensiones: Aleatoria y no aleatoria y dentro de ésta se puede observar otras clasificaciones, siendo estás:

1. Aleatorio Simple: Le da la probabilidad a cada uno de los miembros de una población a ser elegidos. Es uno de los más empleados y recomendado en las investigaciones sociales y educacionales, ya que este principio de darle la oportunidad a cada uno de los miembros de la población a ser elegidos o tomados como muestra, es lo que permite obtener conclusiones en la muestra e inferir lo que pudiera ocurrir, a partir de ésta, en la población, con un elevado grado de pertinencia. Estadísticamente permite inferir a la población los resultados obtenidos en la muestra (Devore, 2000), (Montgomery, 1999), (Siegel, 1997),
2. Aleatorio Sistemático: Se hace una lista de la población a intervalos fijos, bien sea tomando el coeficiente de elevación (ce) como punto de partida; donde:

   V. g: Si la población P = 100 elementos y la muestra

   n= 20, entonces: ¿Qué quiere decir esto?

   Indica que cada vez que se produzcan piezas en múltiplos de 5, será seleccionada una para la realización de determinada medición, etc. elementos u objetos producidos (si se tratara de un proceso de producción de piezas).

   También se puede extraer de la lista cada enésimo caso, este método se emplea mucho en los controles de calidad de producciones seriadas y masivas; pero también puede ser empleado en las investigaciones en general.

3. Aleatorio Estratificado: Es otra variación del aleatorio simple y consiste en subdividir a la población en subgrupos o estratos más homogéneos, de los que se toman muestras aleatorias simples de cada uno de dichos estratos. Hay que evitar que los estratos no se traslapen. (superpongan o que existan elementos de un estrato en otro).

2.1) Muestreo no aleatorio por accidente: El investigador incluye los elementos que le son más convenientes para la muestra.

2.2) Muestreo no aleatorio intencional o de juicio: La idea básica que involucra este tipo de muestra, es que la lógica y el sentido común pueden usarse para seleccionar la muestra que sea representativa de una población. Ej. Selección de expertos por el método de experto.

2.3) Muestreo por cuotas: Ésta se obtiene al especificar las características deseadas de los sujetos que se desea recoger la información y se le dejalibertad al investigador para que le aplique los instrumentos necesarios a las personas con esas características. Ej. Se desea hacer un estudio de una población estudiantil de los estudiantes que han repetido el 6. grado y tiene determinada edad o situación en el hogar.

Longitudinal study

From Wikipedia, the free encyclopedia

A longitudinal study is a correlational research study that involves repeated observations of the same items over long periods of time — often many decades. It is a type of observational study. Longitudinal studies are often used in psychology to study developmental trends across the life span, and in sociology to study life events throughout lifetimes or generations. The reason for this is that unlike cross-sectional studies, longitudinal studies track the same people, and therefore the differences observed in those people are less likely to be the result of cultural differences across generations. Because of this benefit, longitudinal studies make observing changes more accurate and they are applied in various other fields. In medicine, the design is used to uncover predictors of certain diseases. In advertising, the design is used to identify the changes that advertising has produced in the attitudes and behaviors of those within the target audience who have seen the advertising campaign.

Because most longitudinal studies are observational, in the sense that they observe the state of the world without manipulating it, it has been argued that they may have less power to detect causal relationships than do experiments. But because of the repeated observation at the individual level, they have more power than cross-sectional observational studies, by virtue of being able to exclude time-invariant unobserved individual differences, and by virtue of observing the temporal order of events.

Longitudinal studies allow social scientists to distinguish short from long-term phenomena, such as poverty. If the poverty rate is 10% at a point in time, this may mean that 10% of the population are always poor, or that the whole population experiences poverty for 10% of the time. It is not possible to conclude which of these possibilities is the case using one-off cross-sectional studies.

Types of longitudinal studies include cohort studies and panel studies. Cohort studies sample a cohort, defined as a group experiencing some event (typically birth) in a selected time period, and studying them at intervals through time. Panel studies sample a cross-section, and survey it at (usually regular) intervals.

A retrospective study is a longitudinal study that looks back in time. For instance a researcher may look up the medical records of previous years to look for a trend.

Andrew Pettigrew - Ideas Clave

http://en.wikipedia.org/wiki/Andrew_Pettigrew#Key_ideas

Key ideas

Writing about his 1985 book The Awakening Giant, which examines how best to explain the success and failings of ICI, Fairfield-Sonn (1987) says:

"Given the scope of the task Pettigrew sets out to accomplish the likelihood of success seems remote. Yet, the author artfully manages to combine the skills of business historian, methodological critic, and pragmatic counselor to produce a cutting-edge work that should be read by everyone who has an interest in organizational development."

Pettigrew's background in anthropology and sociology seemed to predispose his view that "an organisation's strategy is the result of a process embedded in a context" (2003b). He recalls how when he made his "way across then what was a fairly rickety (and in places non-existent) bridge from sociology by way of organisation strategy" such a view was "an unusual thing" since at the time "those with backgrounds in industrial economics ruled the roost" complete with their "overuse of simple distinctions such as 'strategy formulation' and 'strategy implementation' and 'strategy content' and 'strategy process' research.

Despite his intellectual preference for fewer distinctions between content, process, and context, he still tends to be viewed as a researcher in the process tradition simply because it, as he, is interested in more than static decisions. He argues (2003b) that:

• The link between formulation and implementation is not unilinear but interrelated time
• Understanding the change associated with strategy requires understanding of continuity over time
• Strategy, and its impact on future outcomes, are shaped by power and politics

This view of strategy requires the strategy researcher to be historian, anthropologist, and political analyst.

[edit]Views on methodology

Pettigrew considers his work to have been "to catch reality in flight" (2003b) such that human behaviour is studied in context and by locating present behaviour "in its historical antecedents" (2003b:306). He determines three benefits of such a longitudinal study:

1. Length of time enables appreciation of decision-making in context
2. Each individual 'drama' provides a clear point of data collection
3. Mechanisms that lead to, accentuate, and regulate, each drama can be deduced
4. Comparison and contrast is possible allowing continuity and change to be examined

He claims that "most social scientists do not appear to give much time to time" and that, as a result, much of their work is an "exercise in comparative statics" and therefore recommends strategy researchers follow the approach of historians to "reconstruct past contexts, processes, and decisions" in order to discover patterns, find underlying mechanisms and triggers, and combine inductive search with deductive reason.

Backward masking

From Wikipedia, the free encyclopedia

Backward masking has several meanings:

• The original meaning of the term, in psychoacoustics, refers to temporal masking of quiet sounds that occur moments before a louder sound.
• A similar meaning, in use in cognitive psychology, refers to a phenomenon wherein presenting one visual stimulus (a "mask" or "masking stimulus") immediately after another brief (≤ 50 ms) "target" visual stimulus leads to a failure to consciously perceive the first stimulus.^[1]A similar phenomenon can occur when a masking stimulus precedes a target stimulus rather than following it: this is known as forward masking.^[1] While not consciously perceived, the masked stimulus can nevertheless still have an effect on cognitive processes such ascontext interpretation. It has been shown that visually masked stimuli can elicit motor responses in simple reaction-time tasks (e.g.,Response Priming) independent of their conscious visibility^[2]. It is a widespread belief that masked stimuli can be used for psychological manipulation (see subliminal messages, psychorama). However, the empirical evidence for subliminal persuasion is limited.
• In popular music, "backward masking" incorrectly refers to backmasking, or hiding messages in sound recordings that are audible when played backward.

Temporal masking

From Wikipedia, the free encyclopedia

Temporal masking or "non-simultaneous masking" occurs when a sudden stimulus sound makes inaudible other sounds which are present immediately preceding or following the stimulus. Masking which obscures a sound immediately preceding the masker is called backward masking or pre-masking and masking which obscures a sound immediately following the masker is called forward masking or post-masking. Temporal masking's effectiveness attenuates exponentially from the onset and offset of the masker, with the onset attenuation lasting approximately 20 ms and the offset attenuation lasting approximately 100 ms.

Similar to simultaneous masking, temporal masking reveals the frequency analysis performed by the auditory system; forward masking thresholds for complex harmonic tones (e.g., a sawtooth probe with a fundamental frequency of 500 Hz) exhibit threshold peaks (i.e., high masking levels) for frequency bands centered on the first several harmonics. In fact, auditory bandwidths measured from forward masking thresholds are narrower and more accurate than those measured using simultaneous masking.

Temporal masking should not be confused with the ear's acoustic reflex, an involuntary response in the middle ear that is activated to protect the ear's delicate structures from loud sounds.

Percepoción del tiempo desde lo psicológico

Summary: Time Perception

1. Four factors appear to influence time perception: characteristics of the time experiencer, time-related behaviors and judgments, contents of a time period, and activities during a time period.
2. Time is of greater concern to different cultures and different groups within the same culture. Nonetheless, all people have a number of internal processes that follow circadian rhythms, suggesting the presence of an internal biological clock.
3. In time perception research, one might choose a dependent variable from among several options: (a) time estimation, using common units (mins, secs), magnitude estimation, or rating scales; (b) time production; (c) time reproduction; and, (d) comparisons of time intervals.
4. The contents of a time period influence duration estimates; a time period is judged longer if it is intense, complex, and segmented. Some evidence suggests that a filled time period is perceived as longer than an empty time period, although it appears that this might well be due to expectations derived from the information filling the time period.
5. Activities of the participants influence duration estimates; a time period is judged less accurately if people are performing other tasks simultaneously. Time appears to pass more quickly if people are waiting for an unpleasant event, or if the situation in which they are engaged is pleasant.

http://www.skidmore.edu/~hfoley/Time.htm