LESSON 5

LESSON 5: THE THEORETICAL FRAMEWORK AND THE OBJECTIVES OF THE INVESTIGATION.

The first thing to do is to raise a topic in which we want to come with our research. We therefore propose specific objectives and generally an overall goal; all must be concrete, realistic and measurable.

Next we must formulate a hypothesis; I do it if it is not a descriptive study.

The hypothesis is a statement that relates the variables that I want to study in my work. Each hypothesis has an alternative and another null, and we must also differentiate the dependent variable from the independent to be able to elaborate any hypothesis. 

Let us now proceed with the theoretical framework. First we will formulate the PICO question to facilitate the search of information but the most important thing is to critically evaluate the scientific literature or the tests that are found to determine and to use in our theoretical framework or not.

Although first of all what you have done, the fact that the type of study has been carried out, since each has a number of advantages and disadvantages. They can be analytical, descriptive or experimental.

DESCRIPTIVE

It merely observes and describes a population group or phenomenon by the researcher. It is a prevalence study. They are observational because the researcher does not experience anything, all he does is visualize how a variable behaves. For example, measure the level of stress in a given population.

ANALYTICAL

Cohort study (group of things that have something in common) or follow-up. These designs are studies in which relationships between two phenomena or variables are analyzed. For example: the place of residence and obesity. They can be focused or done in different ways:

Follow-up or cohort study (refers to a group that has something in common) by following the group that can be:

• Prospective: I have a current group of subjects and I will follow them for a while, I also have a hypothesis with a dependent variable and an independent one. So I will classify the study subjects as a function of the independent variable. In one group I put those who present the independent variable and in another group to those who do not. Over time I will observe who develop the dependent variable in each group.

The problem of these studies in order to draw reliable conclusions is that it lasts a long time and during that time other variables can influence. Even so, they are very reliable. They are used for consequences that are short term.

• Retrospective or historical: it is a question of classifying a cohort in exposed and not exposed to the independent variable and observe over a period of time if they have developed the disease. But this cohort is old, this data has not collected the researcher, has collected another person and do not know if they are reliable. Therefore a historical cohort and a prospective one do not have the same reliability.

Case-control study: based on doing the exact opposite of the above, I have a group of subjects that present the dependent variable (lung cancer patients) and I want to know if the tobacco influences. Then I inquire into your past. Inquiring whether they were exposed to the independent variable (tobacco) and comparing it to a group of subjects similar in age, sex ... and who do not have cancer, in this group I have to find out whether or not they have been smokers.

EXPERIMENTAL

They are the same as a prospective study starting from the independent variables to the dependent ones. In what varies, the independent variable is introduced by the researcher. In these studies the exposure is subjected to chance.

Reliability: clinical trials - cohort studies or prospective follow-up - cases and controls - historical cohort studies - descriptive studies.

LEVELS OF EVIDENCE

• Level of evidence I: Obtained from at least one controlled, adequately randomized clinical experiment (without subjects who have decided to leave the experiment), or a meta-analysis (high quality studies).

• Level of evidence II: Obtained from at least one controlled, adequately randomized clinical trial or high quality meta-analysis but with high probability of false positive or false negative results.

• Level of Evidence III:

Level of Evidence III.1: Obtained from controlled and non-randomized experiments,               but well designed in all other respects.

Level of Evidence III.2: Obtained from well-designed observational analytical studies             using a prospective cohort, with more than one research group.

Level of evidence III.3: Obtained from historical cohorts. It is the most frequent.

• Level of evidence IV: Opinions of respected authorities based on unquantified clinical experience, or reports of expert committees.

APPLICATION OF CONCLUSIONS TO PRACTICE:

Of the previous levels of evidence, five grades of recommendation emerge:

Grade of recommendation A: There is satisfactory evidence (usually level I) that supports the recommendation for the intervention or activity under consideration, I must recommend it.

Grade of recommendation B: There is reasonable evidence (usually level II, III.1 III.2) that supports the recommendation for the intervention or activity under consideration.

Grade of recommendation C: There is poor or little evidence (usually level III.3 or IV) that supports the recommendation for the intervention or activity under consideration. In this case I would not recommend it as much.