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Statistics is study of collection, organization as well as interpretation of data. It mainly deals with entire aspects on this, which includes planning data collections in terms of design of the experiments and surveys. Statisticians are people who are particularly versed in methods of thinking necessary in successful applications of statistical analysis. In scientific discipline, the word statistics is singular, mainly indicating that statistics is an art. In some instances, statistics is referred to as mathematical science that pertain collection, analysis, explanation or interpretations and presentations of data. Due to its empirical roots and focus on application, statistics is considered to be distinct mathematics science rather than branch of mathematics. Descriptive statistics is used in describing or summarizing collections of data.

This is vital in research, in communicating results of experiments. In addition to this, patterns in data can be modeled in ways that can account for uncertainty and randomness in observations. They are used in drawing inferences about processes or populations being studied called inferential statistics. Inference is important element of scientific advances, as it gives predictions, based in data, for where theories logical lead. Statistics is highly associated to probability theory, the difference being that in probability theory, one have to start firm certain given parameters, of the total population in deducting probability pertaining to given samples, but statistic inferences moves  opposite directions, inductive inferences from samples to parameters of total or larger populations.

Generally, when statistical techniques are applied in the correct manner, the results are mostly difficult to interpret especially for those who lack expertise. Statistical significance of trends in data, measuring the extents to which trends could be caused by random variations in samples, may sometimes agree to intuitive sense of its significances. This paper will critically evaluate experimental and observational statistics, which are considered integral parts of statistics.

Experimental and observational statistics

The common goal of statistical research projects is to help in investigating causality, particularly in drawing conclusion on effects of changes in values of independent variables on the dependent variables or responses. The two major types of casual statistic studies are the observation and experimental studies. In both areas of studies, the effects of difference of independent variables on behaviors of independent variables are usually observed. The main difference between experimental and observational statistics lies entirely on how studies are actually carried out.

Experimental statistics

Lindley, 109 experimental studies in statistic involves taking measurements of systems under studies, manipulating the systems and taking additional measurements. This is done by using similar procedures in determining if manipulations have modified values of measurements.

Steps of statistical experiments

There are some basic steps that are involved in statistical experiments. This includes


Planning the research entails finding numbers of replicate of the study, using some given information. This includes preliminary estimates in regard to the sizes of treatment effect, alternative hypotheses as well as estimated experimental variability. Consideration of selection of experimental ethics and subjects of the research is crucial. In order to prevent unbiased estimates of the difference in treatments of the effects, it is recommended that experiments should compare more than one new treatment.

Design of experiments

Design of experiments, carried out using blocking in order to reduce influence of the cofounding variables as well as randomized assignments of treatment to subjects. This is done in order to allow unbiased estimate of the treatment effect and experimental errors. In experimental designs, experimental protocol is done by the statisticians in order to guide performances of experiments which specify primary analysis of experimental data.  Other procedures useful in carrying out experimental statistics includes performing the experiment, further examination of data sets in secondary analysis in order to suggest new hypothesis for future studies as well as documentation and presentation of the results of study among others. When experimental research is used to study   human behaviors, special concerns usually arise. In the  famous Hawthorne study, where the researcher   examined changes to working environment by initially measuring the productivity then modified illumination in an area and then checked whether  if illuminations had any effect on workers productivity. Although the study had a lot of experimental errors it was detrimental in improvement of experimental statistics.

Observation statistics

Observational study involves gathering and investigation of data and correlations between response and predictors. It does not involve experimental manipulations which are found in experimental statistics. Henk, 57 observation study in statistics usually draws inferences on possible effects of treatments on the subject, where assignment of the subject into treated group versus control groups is normally outside the controls of investigator. It is in contrast to controlled experiments like the randomized control trials, where subjects are randomly assigned to treated groups or control groups prior to start of treatment.

Importance’s of observational statistics

Ethical standards

In most cases randomized experiments usually violates ethical standards. For example, if one is to investigate breast cancer-abortion hypothesis, postulating casual links between induced abortions and incidences of abortions, one would require large numbers of treatment groups. This would in turn result to various cofound as well as source biasness leading to blind experiments. This makes it important to conduct uncontrolled experiments by observation statistics.

Requisite influence

In controlled experimentations, the investigators may lack requisite influences which does not happen in uncontrolled experimentations. For instant, if a dentist wishes to study public heath effects of community wide ban on smoking in public in door areas the scientist would have to randomly pick sets of communities in treatment groups in the case of controlled experiments. However the scientist may lack political power to cause the precisely those communities in randomly selected treatments group pass smoking bans. In observation study, investigators would start with treatment groups comprising of the communities where the ban has been affected.

Practicability of observation study

It is important noting that, randomized experiments are often impractical. For example if a scientist would wish to study the link between rare groups of symptoms and   particular medication arising side effects, then randomized experiments would be highly impractical due to rarity of the effects. However, observation study, researchers would start with group of symptomatic subject as well as work back wards to discover those who give medication and later development of the symptoms. One of the major challenges which are faced when conducting observation studies is drawing inferences which are acceptably free from the influence by overt biases and accessing the influence of the potential hidden biases.  Observers in uncontrolled experiments or processes records potential factors and data outputs the goal being determining effects of factors. In some instances, the record factor may fail to directly cause differences in output. As the numbers of record factors rise, likely hood increases that one or more recorded factors will correlated with data output through chances. In observational studies, investigators normally use the PSM (propensity score matching), where the propensity score is defined as conditional probability of treatments given backgrounds variable as

P(x) \ \stackrel{\mathrm{def}}{=}\ \Pr (T=1 | X=x). Hacking, 33

Treatment assignment is conditionally unconfounded if treatments are independent of the potential outcome conditional on X. Thus it can written compactly as

T \perp Y(0), Y(1) \,|\, X   Hacking, 34

Where \perp, usually denotes the statistical independence


It is clear that statistics  hardly gives  yes or no answer  to question asked. Interpretations often come down to levels of statistical significances applied to numbers and refer to probability of value accurately rejecting null hypothesis . This is often referred as p- value, which is the probability which obtains test statistics at least extreme as one that was observed, assuming null hypothesis is true. Generally, referring  to statistic significance does not necessarily  mean   the overall results are important real word terms. In real sense, statistics is highly related to probability theory, which is often grouped with. The main difference being that, in probability theory,  one have to start from given parameters of total populations in deducing probabilities pertaining top the samples, but statistical  inferences moving in opposite directions, inductive inferences from the sample to parameters of the total or larger population. In conclusion it is worth to note that, Experimental and observational studies in statistics have played a great role in the modern times as far as scientific researches among other notable aspects are concerned. 

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