Methods qualitative vs quantitative

^{Cook (1979)}, pointed out that there are two methods for collecting data: qualitative and quantitative. The more obvious distinction to be drawn between the two is that quantitative methods produce numerical data and qualitative result information or descriptions of situations, events, people, interactions, and observed behaviors, direct quotations from people and extracts or passages documents, correspondence, records and case studies. Quantitative research is that which collect and analyze quantitative data, meanwhile quantitative which prevents quantification; however, records are made through narrative, participant observation and unstructured interviews.

^{Fernández (2002)} indicates that qualitative research seeks to identify the profound nature of reality, their relationships and their dynamic structure, on the other hand quantitative research attempts to determine the strength of association or correlation between variables, generalization and objectification the results through a sample for inference in a population. Qualitative methods for data collection play a very important role in impact assessment because they provide valuable information to understand the processes behind the results. According to the ^{World Bank (2003)} can be used to improve the quality of the survey-based quantitative assessments as they help to generate assessment hypotheses, strengthen the design of questionnaires for surveys, and broaden or clarify the findings of the quantitative evaluation.

Meanwhile ^{Grawitz (1975)} posed as a question whether the fact can the social sciences take advantage of the instrument of quantitative methods? In this regard, it did not find a conclusive answer, since certain sectors of some social sciences lend themselves better than others to a quantification. In the social sciences ^{Grawitz (1975)} indicated that there is an error in the passage from the qualitative to the quantitative, since the second method depends on the data collected primarily by the first, which are collected and processed. Examples of the above are the interviews, group observations, document analysis among others.

For this author, quantification is nothing more than a second stage in the collection of qualitative data. Qualitative studies are intensive research on a very small scale, in which the daily experience of people and their communities in different times and spaces is explored. In these works, the position of the investigator, their experiences, perspectives and prejudices are significant aspects in the development and results of research (^{Philip, 1998}).

^{Reichardt and Cook (1986)} indicated that qualitative research offers the opportunity to focus on finding answers to questions that focus on the social experience, while quantitative research is characterized by a global conception based in logical positivism with a particularity is oriented to the objective results. These authors mention that qualitative methods are not only quantitative questions and answer only to conclude by saying that there is no fundamental clash between the goals and capabilities of the methods or qualitative or quantitative data.

There are different ways of doing science, especially methods which lead to comprehensive explanation and understanding of the phenomena explanatory study, both perspectives are necessary and both can work together in a complementary (^{Álvarez, 1986}). Similarly, ^{Calero (2000)} concluded that the use of either method depends on the moment that the researcher is interested in privileging (generation of theory or transformation of reality and topic that is chosen to investigate).

^{Orozco (1997)} mentions that social studies from the Second World War had much quantitative emphasis especially statistics, as the winners of the war wanted to preach and persuade to mathematics the whole world, hence communication sciences and culture adopted quantitative methods as a working tool, from the 40’s the United States of America sponsored many social research with emphasis on those methods. The quantitative studies were becoming more obsolete than ever generalizations were made from smaller samples.

Advantages and disadvantages of qualitative and quantitative methods

The advantages and disadvantages of quantitative and qualitative methods are shown in the Table 1 based on ^{Reichardt and Cook (1986)} and supplemented by ^{Fernández (2002)}.

Table 1 Advantages and disadvantages of qualitative and quantitative methods. 

In both methods requires intentionality and systematize information, the use of instruments in the quantitative are those that guide the research and in the qualitative are the processes that guide. In quantitative methods data can be accumulated and compared to have common data, while qualitative methods can cover the entire spectrum of a population whose distribution is considered normal and are also personalized. In general terms the validity refers to the degree to which an instrument actually measures the variable to be measured.

Validity is a concept which can be different types of evidence: content validity which refers to the degree to which an instrument reflects a specific content domain which is measured, the validity criterion establishes the validity of an instrument of measurement by comparing it with some external criterion and the validity of the construct refers to the degree to which a measurement is consistently related to other measurements according to hypotheses derived theoretically and that concern the concepts or construct.

^{Hernández et al. (2010)} indicates that an experiment should be sought primarily internal validity; i.e. confidence in the results, if this is not possible there is a real experiment, the internal validity is only part of the validity of a study, since it is desirable that the experiment or study also have external validity, by the latter we must understand how generalizable are the results of an experiment to non-experimental situations and to other subjects or populations.

Quantitative methods are stronger in external validity as a representative sample of the population make inference of said population from a sample with a confidence and precision defined, thus limiting the methods qualitative is the difficulty to generalize, on the other hand quantitative research with the hypothesis tests not only eliminates the role of chance discard or reject a hypothesis, but to quantify the importance of a phenomenon by measuring the relative risk reduction (^{Calero, 2000}).

^{Fernández (2002)} indicates that there is more quantitative than qualitative research today, arguing that the use of this method is not a product of chance, but rather of the evolution of the scientific method, since with quantification it increases and facilitates the understanding of the universe that surrounds us, concludes by stating that the use of both procedures in an investigation would probably help to correct the biases of each method.

Regarding reliability in social research using quantitative methods, so that the results are more reliable the required sample size should be increased, therefore the sample size is directly proportional to the desired reliability (^{Snedecor and Cochran 1967}). On the other hand, the same authors indicate that a higher sample size will be required at higher precision; the sample size is directly proportional to the accuracy but inversely proportional to the value of accuracy; i. e., that more accurately sample size will be smaller. ^{Grawitz (1975)} indicated that the precision of an instrument is usually defined by their sensitivity to the variations that must register.

The criteria for selecting a particular method will depend on various factors among which:

Type of research problem, the nature of the object and subject of study.

Time and the possibility of carrying out one or more research on all the costs.

Information accuracy is achieved greater precision in quantitative.

The users or the audience to which the results are directed.

The difficulty to obtain information.

The precision of an instrument is usually defined by its sensitivity to the variations to be recorded, in the case of the social sciences, it will be the accuracy with which the position of an individual is placed in relation to the characteristic to be measured, for example an opinion poll will only give a proportion of supporters or related subjects, nonpartisan or without opinion. Hence accuracy validity and reliability closely aligned (^{Grawitz, 1975}). Measurement is fundamental in experiments and studies of the social sciences, there are scales of measurement, among them are:

Nominee: who can name a subject or object, for example: men and women

Ordinal: as the name implies have an order, which can be up or down.

Interval: groups of individuals ranges where the distance between them is arbitrary.

Proportional: the distance between individuals in a population is the same.

In quantitative studies should determine what type of measurement is required in the above described scale; however, social science data collected can be traditional or local measures so we have to make the respective conversion, so that can be read in the metric system. There must be a compatibility of concepts between the researcher and the interviewee, especially when the answers are obtained in regional measures. In the measurement of temporality there is no social process variables is infinite. Every measurement must have two essential requirements.

Reliability and validity. The reliability of a measurement refers to the degree to which their repeated the same subject or object application produces similar results.

However, reliability can be affected by various factors among which improvisation, because choosing an instrument lightly and development of an instrument either shows a lack in with knowledge and is therefore a tool bit reliable and invalid. Another factor that affects reliability is the development of instruments abroad without being validated in the context where the research will be developed. Therefore, the concepts culture and time are valid for this case. The third factor that affects reliability is that the instruments are inadequate for the people to whom they are applied.

The fourth factor that affects the reliability of an instrument is the conditions in which the instrument is applied, such as cold, heat, wind or rain, noise among others. In summary reliability varies according to the number of items or subjects included in the study, the more older items will reliability, ^{Snedecor and Cochran (1967)} and subsequently ^{Hernández et al. (2010)} coincide in the above.

Applicability of instruments, this depends on the nature of the study or investigation, since not all instruments can be used for all types of investigations, such as depth interview only it focuses on an individual while a survey can represent all a population. On the other hand, participant observation is useful as social phenomena and life cycles are investigated, anthropologists have in this technique a valuable tool.

All scientific research is connected between the research topic and the purpose of the investigation, about ^{Dieterich (1999)} mentions that the research topic is expressed in a statement or proposition, while the object of research is the real phenomenon the sentence or phrase refers study. Therefore, the object of research is an aspect of reality, in which our interest in knowledge is concentrated and cannot be explained immediately or without use of theory. Therefore, ^{Dieterich (1999)}indicates that the object of study in a scientific analysis is a real, verifiable phenomenon that exists in the universe independently of the interest of the knowledge and subject of research that a person might have on it.

Social science is said that the research object changes when a part of your reality is modified by internal or external factors. For example: s i the object of research are social relations between actors in a particular region, then qualitative methods are vital; on the other hand, if what you want is a typology based on productivity actors the same region, then qualitative methods are indicated. It does not mean that one is exclusive of the other, but the dynamics of the research object causes the investigator’s decision to use either method according to the purpose of his study.

Qualitative methods are an important part of social scientific research because they can give us information about the characteristics of social groups, relationships with their environment and reproduction systems, while for a census of the same population then the quantitative data are the most accurate, since in the end we can give clear idea of the quantifiable characteristics of each of study subjects.

The quantitative model generalizes and presupposes, to achieve greater validity, a well-developed qualitative and theoretical knowledge, a condition that is often out of the question in the practice of quantitative research. Criticism of quantitative research is not directed against its method in general, but against the unique application of it to investigate social reality. Before establishing quantitative measurement, it is worthwhile to qualify the problems and needs and both determine priorities as factors to be investigated. From there one can resort to the measurement of certain variables through the determination of the indicators. Also note here the questions that need to be raised such as:

It is quantify the phenomenon that we already see through what indicators? Is it precise the information that we get and is valid as well as reliable? Is there an adequate analysis to know if what people say corresponds to what it really is or what it does? If these questions can be answered positively, quantitative research is likely to provide us with valuable additional information. The previous question leads us to the position of holding that are not incompatible qualitative method and quantitative, but there is a complementarity, although there is between the two a marked difference because these two methods can serve objectives very different, trying the same subject ^{Fernández (2002)}.

Some measuring instruments

The following description of the main instruments used in social research and its applicability were taken from: while ^{Orozco (1997)}; ^{Pardinas (1999)}; ^{Dieterich (1999)}; Sail (2001); ^{Fernández (2002)}; ^{Hernández et al. (2010)}; ^{World Bank (2003)} among others, it is worth mentioning that not all the instruments that exist, however set out the most frequently used by researchers. Of the qualitative instruments are:

Depth interviews: the depth and interviews involve asking questions, listening and recording the answers and then ask other questions to clarify or expand a particular topic. Questions are open and interviewees must express their perceptions in their own words.

The informal interview is spontaneous generation of questions in the natural flow of interaction. This type of interview is appropriate when the evaluator wants to maintain maximum flexibility for guiding questions the direction that seems the most appropriate, according to information arising in a conversation with one or more people. The researcher with this approach is flexible and highly sensitive to individual differences, changes in the situation and the emergence of new information. However, a weakness is that it can generate less systematic data, whose classification and analysis will be difficult and slow.

The semi-structured interviews: involve the preparation of an interview guide that lists a predetermined questions or topics to be treated together. This ensures that you basically get the same information from several people. Even so, there is plenty of flexibility. The advantage of the style of the interview guide is the fact interviewing different people become more systematic and comprehensive, as the issues to be discussed are delineated. The weakness of this approach is that it allows the interviewer guide topics or topics of interest that were not anticipated at the time of the preparation of the guide.

Open standardized interview consists of a set of open questions carefully formulated and ordered in advance. The interviewer asks the same questions to each of the interviewees, essentially with the same words and in the same order. This type of interview may be especially appropriate when there are several interviewers and the evaluator wants to minimize the variation of the questions.

Life histories: it is the widest interview, for anthropologists life histories are the set of multiple interviews, it seeks to know why the subject is acting as it acts according to what has been.

Case studies: these are made for comparative purposes, is to be an in- depth study is the effort to integrate into an object of research all constituent information of the object and not just part of the information.

Survey: puts the respondent in a passive role. He feels examined, even by a strange being and will be unlikely to respond in all respects, then in a discussion with acquaintances. For the characteristics of the survey characteristics, the unique character of the person, of a process or a social phenomenon, dividing them into a number of features, elements or indicators and then add them is lost. The survey method is too static. The survey captures what in a given moment has manifested but does not assimilate in the short term the changes that can occur in society. Therefore, the survey will not be useful to detect sudden and large changes, which are very frequent in societies.

Content analysis or textual or documentary analysis: a technique for studying and analyzing communication in an objective, systematic and quantitative manner, and allowing valid and reliable inferences of data with respect to its context.

Ethnographic observation: which can be participant or non-participant, does not necessarily have to be of one type or another but depends on the interests and the ends of the investigation.

Of the quantitative methods the most outstanding are: experiments: based on the typology of ^{Hernández et al. (2010)}, there are three types of experiments: the pre-experiments, the real experiments and the quasi-experiments, in the first the control is minimal; in the second it must meet two requirements to achieve internal control and validity; the manipulation of one or several independent variables and the equivalence of the groups. In the quasi-experiment the groups under investigation are already formed and therefore are not the product of a random distribution, but also the independent variables can be manipulated.

The study of social processes can be approached with methods and techniques of quantitative or qualitative collection, ^{Zepeda and González (2001)} after substantively analyzing the nature of the construct or object of research in the social processes, arrive at a conclusion that there is no agreement on whether the difference between qualitative and quantitative methods is epistemological or technical, since the construction of the object is anchored in the prior theoretical knowledge of the researcher. ^{Orozco (1997)} indicates that in the study of political processes one of the implications of the political perspective is the commitment of the researcher to the object of study, since not only is this not far from the object of study but is involved, which does not exempt him from falling into subjectivities.

Under this same process but in quantitative research, where the events of reality to be investigated are verified, quantified and can be or not to know or used in any way. In a quantitative research the researcher applies the techniques appropriately, develops the analyzes according to the scientific knowledge and this does not cause him to take on greater responsibility as long as he does his work properly. This may result in the information being manipulated according to the interests of the political groups or to conduct a policy in accordance with the data and results presented by the quantitative researcher.

But the manipulation of qualitative data in political processes also occurs, for this the bases and ethical foundations of the researcher must be well entrenched and their commitment to the object of investigation must be very important for him. ^{Orozco (1997)} mentions that the greatest manipulation is in what is investigated and what is left out of the interest and scope of research. The implications of qualitative research are that they open on the one hand the possibility to obtain sustenance from the political action of society and on the other to involve new agents of transformation or political action. In this regard ^{Gutiérrez (1997)} indicated that new political and social actors are emerging in the political and social sphere, marking a new relationship between the Mexican State and civil society, including the Barzón Movement, The Zapatista Movement of Chiapas, the “Indios” and “Pochos”, new religious groups, lay movements and citizenship and the magisterial movement among others.