Basics in Experimental Research M.Prasad Naidu MSc Medical Biochemistry, Ph.D,.

Dynamic nature of this U n i v e r s e :

Dynamic nature of this U n i v e r s e

this very continuous change in Nature brings - uncertainty and - variability in each and every sphere of the Universe:

this very continuous change in Nature brings - uncertainty and - variability in each and every sphere of the Universe

This uncertainty and variability prevalent in nature makes it difficult to satisfy our inner-urge of -acquiring knowledge :

This u ncertainty and v ariability prevalent in nature makes it difficult to satisfy our inner-urge of - acquiring knowledge

Encountering the uncertainty and variability - thereby understanding their role in - rational explanation of the facts becomes the basic feature of sciences :

Encountering the uncertainty and variability - thereby understanding their role in - rational explanation of the facts becomes the basic feature of sciences

We by no mean can control or over-power the factor of uncertainty but capable of measuring it in terms of Probability :

We by no mean can control or over-power the factor of uncertainty but capable of measuring it in terms of Probability

This measurement helps a lot - in experimentation and - making out inferences with minimum interference of the chance or luck factor :

This measurement helps a lot - in experimentation and - making out inferences with minimum interference of the chance or luck factor

. It is true in the case of variability also, which once again can’t be eliminated but easily measurable. The measures of deviation & central tendency play a key role in all research. :

. It is true in the case of variability also, which once again can’t be eliminated but easily measurable. The measures of deviation & central tendency play a key role in all research .

Biological Observations :

Biological Observations Though this universe is full of uncertainty and variability, a large set of experimental / biological observations always tend towards a Normal distribution .

Inferential Statistics :

Inferential Statistics This unique behavior of data is the key to entire inferential statistics.

Population Probability Distributions:

Population Probability Distributions such as; Normal Binomial Poisson Rectangular

Sampling Distributions:

Sampling Distributions like Chi-square, Student’s ‘ t’ and ‘ F’

PowerPoint Presentation:

Mean -3s -2s +2s +3s 95.5% 99.7% The role of Central tendency and Deviation

Population & Sampling Distributions:

Population & Sampling Distributions frequently used for probability calculations and also for testing the hypotheses through various tests of significance

Relativity:

Relativity Understanding the Relativity Component hidden invariably in most of the scientific explanations is still more important

Most of the qualitative characteristics involved in experimentation either as independent or dependent variables, are measured in relative terms - Defining absolute zero pain, stress or measuring health and disease or :

Most of the qualitative characteristics involved in experimentation either as independent or dependent variables, are measured in relative terms - Defining absolute zero pain, stress or measuring health and disease or

Even quantitative variables like temperature - where absolute zero is difficult to know, are the examples of inherent relativity in measurements and require special attention while making out inferences based on such measurements.:

Even quantitative variables like temperature - where absolute zero is difficult to know, are the examples of inherent relativity in measurements and require special attention while making out inferences based on such measurements.

Inductive reasoning::

Inductive reasoning : Repeating the experiments essentially under the same conditions and keenly observing the outcome each time and relating them to derive a fact is the system followed in inductive reasoning in science

Deductive Reasoning::

Deductive Reasoning : ‘Pure Mathematics’ is an example of ‘formal science’, or deductive reasoning where the conclusions are derived on the basis of existing facts, definitions, theorems, and axioms .

The Principles and decision-making :

The Principles and decision-making If inductive reasoning helps us in developing the principles that can be generalized, the deductive reasoning guides us in generalized decision-making .

Measurement Scales:

Measurement Scales Nominal scale Ordinal scale Interval scale Ratio scale

Error and Bias:

Error and Bias No experimentation or observation can be totally free from errors and escape from bias. But we must identify and recognize them for their elimination as for as possible or to control and minimize the effect

Measurements even being valid, if lack in precision and accuracy, irrespective of the magnitude or quantity of deviation from the intended measurement, are called errors. - One sided repeated errors or systematic errors are called bias. :

Measurements even being valid, if lack in precision and accuracy, irrespective of the magnitude or quantity of deviation from the intended measurement, are called errors . - One sided repeated errors or systematic errors are called bias .

Selection or allocation biases, - Measurement bias, - Instrument bias, - Inter & intra investigator or - Observer’s bias, - Misclassification bias etc. are some of the frequently encountered bias :

Selection or allocation biases, - Measurement bias, - Instrument bias, - Inter & intra investigator or - Observer’s bias, - Misclassification bias etc. are some of the frequently encountered bias

We know that the techniques of blinding, randomization, replication, standardization, selection of controls and to a great extent the experimental designs do help us to overcome some of them.:

We know that the techniques of blinding, randomization, replication, standardization, selection of controls and to a great extent the experimental designs do help us to overcome some of them .

variable:

variable A variable takes on or can assume various values But the same quantity may be a constant in some situation and a variable in another

Classification:

Classification The variables may broadly be classified in a number of ways such as, continuous & discrete, qualitative & quantitative, random & non-random etc.

terminologies and role of variables :

terminologies and role of variables Various models use different terminologies to explain the role and status of variables

terminologies and role of variables:

terminologies and role of variables For example in epidemiology we use the terms ‘independent, dependent and intervening variables’; or parallel to that ‘cause, effect and confounding / interacting variables’; in certain situations the same are called ‘input, process and output variables’ ;

terminologies and role of variables:

terminologies and role of variables In forecasting the nomenclature preferred is ‘ predicting, predicted and disturbing variables’ ; in laboratory situations we pronounce them as ‘ experimental, outcome and chance / random variables’ and so on .

Changing role of Variables:

Changing role of Variables A dependent or outcome variable can serve as an independent or input variable in another process

Changing role of Variables:

Changing role of Variables Researchers do experience hundreds of other terms used invariably to explain very specific role assigned to a variable in a particular situation, such as, pseudo variable, or dummy, proxy, nuisance, substitute, culprit, treatment, response, extraneous, manipulated and complex variables etc

Clarity in knowing the variables:

Clarity in knowing the variables The clarity in knowing the variables of interest to be considered in a particular study helps a lot in recruitment of research tools, techniques and methods to be used during experimentation and use of statistical tests at the end of the study .

Experimental Designs The purpose of an experimental design is to enhance the power of inference making by either; - eliminating undesired independent variables from the site of experiment or minimizing their effect during the experimentation, and - also to allow the desired independent (or experimental) variables to their full exploitation for manipulations by the research investigator :

Experimental Designs The purpose of an experimental design is to enhance the power of inference making by either; - eliminating undesired independent variables from the site of experiment or minimizing their effect during the experimentation, and - also to allow the desired independent (or experimental) variables to their full exploitation for manipulations by the research investigator

Experimental Designs:

Experimental Designs Experimental designs also help in sequencing the deployment of experimental tools, techniques and methods. completely randomized and randomized block designs are a few examples. Clinical trials with or without randomization and blinding, self-controlled and without control or crossover designs are frequently used in clinical settings.

The Sample and Sampling::

The Sample and Sampling : A study of entire population is impossible in most of the situations. Sometimes, the study process destroys (animal sacrifice) or depletes the item being studied. In such situations the only alternative is sample study.

Advantages:

Advantages sample results are often more accurate , apart from being quick and less expensive

PowerPoint Presentation:

If samples are properly selected, probability methods can be used to estimate the error in the resulting statistics. It is this aspect of sampling that permits investigators to make probability statements about the observations in a study

Sample size and sampling error :

Sample size and sampling error The sample size has to be directly proportional to the heterogeneity in the population, whereas, the sampling error is always inversely proportional to it.

Probability sampling:

Probability sampling The techniques of sampling may be classified as “Probability sampling” such as; - Simple random sampling, - Stratified, cluster, systematic, - Multi-stage and multi-phase sampling; and

Non-Probability sampling:

Non-Probability sampling such as; Convenience sampling, Inverse or quota sampling, Judgment and purposive sampling etc. But non-probability sampling findings are usually not qualified for any generalizations as they lack to be representative of the entire population.

Power of a study:

Power of a study It is not only the sample-size but also the sampling method equally responsible for the power of a study.

To summarize:

To summarize bigger does not always mean better or more powerful in making inferences .

PowerPoint Presentation:

For this reason, investigators must plan the sample size appropriate for their study prior to beginning research

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