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Statistics
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Introduction to the Degree in Statistics. Source: Wikipedia (CC BY-SA 4.0).
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What you need to know
Read the full theory →Definition, applications, and branches of statistics
- Definition: Study of variability and random processes under probability laws
- Use in factual sciences: Collection, organization, analysis, and interpretation of data
- Methodological objective: Extracting conclusions from samples and inferences about populations
- Descriptive statistics: Summary and visualization of data (e.g., mean, standard deviation, histograms)
- Inferential statistics: Generation of models, predictions, and inferences about populations
- Inferential techniques: Hypothesis testing, estimation, forecasting, correlation, and regression
- Subdivisions of inferential statistics: Parametric and non-parametric
- Mathematical statistics: Establishes the theoretical foundations of the techniques
- Differentiation: "Statistics" refers to the summary of descriptive results
Historical evolution and origin of statistics
- Origin: Gottfried Achenwall (1749), "science of the State".
- Current meaning: Introduced by Sir John Sinclair in the 19th century.
- Bibliographic relationship: Located next to demography (Melvil Dewey).
- Babylon (3000 BC): Clay tablets for agricultural production and trade.
- Egypt (3050 BC): Censuses for pyramid planning and resource management.
- China (2238 BC): Yao's general census (agricultural, industrial, and commercial).
- Greece (594 BC): Censuses for taxes, military service, and voting rights.
- Rome: Records of births, deaths, and wealth.
- Mexico (1116): Census ordered by King Xólotl.
- Middle Ages: Work of Isidore of Seville (Originum sive Etymologiarum).
- Spain (Early Modern Period): Censuses of Pecheros (1528), Obispos (1587), Millones (1591), and Aranda (1768).
- England (1500s): Data multiplication due to the plague.
Historical evolution of probability theory and statistics
- Origin: Pascal-Fermat correspondence (1654)
- First scientific treatment: Huygens (1657)
- Mathematical consolidation: Bernoulli (1713) and de Moivre (1718)
- Modern fundamental model: Kolmogorov
- Theory of errors: Simpson (1755) introduced the discussion of errors and the axiom of equal probability
- Combination rules: Laplace (1774) deduced formulas for the mean and the law of error ease
- Maximum product principle: Bernoulli (1778)
- Least squares: Published by Legendre (1805), Adrain (1808), and Gauss (1809)
- Practical application: Gauss (1801) predicted the location of Ceres
- Social statistics: Quetelet introduced the concept of the "average man"
- Rigorous discipline: Galton and Pearson in the 20th century
- Galton's contributions: Standard deviation, correlation, and regression
- Pearson's contributions: Correlation coefficient, method of moments, and Pearson distributions
- Institutions: Biometrika and the statistics department at University College London
- Variance: First use of the term by Fisher (1918)
- Experimental design: Fisher (1935) developed rigorous models and the concept of sufficiency
- Biology: Fisher's Principle (sex ratio) and Fisherian runaway (1930)
Foundations, applications, and methods of statistics
- Definition: Statistics is a formal science and a subfield of mathematics applied to factual sciences.
- Unit of study: Can be an entire population, a process, or a time series.
- Sample: A selected subset of the population to facilitate data collection.
- Purposes of analysis: Description and inference.
- Correlation: Joint variation of two variables; does not imply causation.
- Confounding variable: A third variable not taken into account that may explain an apparent correlation.
- Representativeness: A necessary condition for extending sample conclusions to the population.
- Statistical theory: The branch that uses probability theory and mathematical analysis.
- Mathematical assumptions: A mandatory requirement for the validity of any statistical method.
- Statistical significance: Measure of the extent to which a trend may be caused by random variations.
- Causality: The study of the effect of independent variables on dependent variables.
- Types of causality studies: Experimental and observational.
Levels of measurement, statistical techniques, and population concepts
- Nominal Level: Grouping into classes without interpretable order.
- Ordinal Level: Possesses an interpretable order but imprecise differences.
- Interval Level: Constant unit and measurable distance; arbitrary zero.
- Ratio Level: Highest level; possesses an absolute zero (absence of magnitude).
- Statistical tests: Include ANOVA, Pearson, Spearman, χ², Student's t, and Mann-Whitney U.
- Population: The total set of values; its complete analysis is a census.
- Finite population: A limited number of elements.
- Infinite population: An unlimited number of observations.
- Sample: A subset of the population; its selection is sampling.
- Representative sample: Must contain the essential characteristics of the population.
- Parameter: Numerical measure of the population (μ or σ).
Evolution of statistics, misuse of data, and inference methods
- Computational impact: Transition from linear models to neural networks, decision trees, and multilevel models.
- Resampling methods: Growth of permutation tests, bootstrap, and Gibbs sampling.
- Chaos theory: Established in the U.S. with 350 books in 1997 and applied in physics and social sciences.
- Data bias: Introduced by non-random selection or selective removal of outliers.
- Professional requirement: It is proposed that statistics be a regulated profession for graduates in Mathematics or Statistics.
- Type I error: A common consequence of technical ignorance in data interpretation.
- P-hacking: The practice of searching for significant associations without a prior hypothesis, affecting reproducibility.
- Classical inference: Risk of overestimating the importance of small differences in large samples.
- Scientific inconsistency: Caused by the use of small samples and poorly applied statistical techniques.
Critiques of hypothesis testing and methodology in statistics education
- P-value criticism: summarizes evidence of the effect but not its size.
- Confidence intervals: indicate effect size and uncertainty.
- Bayesian methods: an alternative to hypothesis testing, also criticized.
- Type I and Type II errors: create tensions in drug approval.
- Effective teaching: requires concrete examples and relevant problems.
- Qualitative-quantitative linkage: allows using descriptive details to quantify and generalize.
- Triangulation of results: decreases the fallibility of data.
- Curricular integration: quantitative reasoning must be included in core courses.
- Wikipedia usage: visit analysis helps identify curriculum topics.
- Practical approach: prioritizes test selection, interpretation, and free software.
Statistical Law and Statistical Criminology
- Statistical Law: a legal discipline that studies trends and frequencies of mass phenomena.
- Objective: to regulate social life to make it fairer and less manipulable.
- Main function: to provide data for social regulation with reliability and validity.
- Use in justice: a fundamental tool where data can determine innocence or prejudice.
- Risk: misuse of statistical data in judicial proceedings.
- Statistical Criminology: a discipline that provides research principles and techniques for more accurate trials.
- Context: scarce rigorous statistical approaches in Latin American countries.
Flashcard preview (6 of 40)
- 01
Statistics studies the variability of phenomena and the [____] processes that generate them.
random
- 02
In factual sciences, what is the objective of descriptive statistics?
To organize and describe the characteristics of a dataset.
- 03
Inferential statistics is used to draw inferences about the [____] under study.
population
- 04
Inferential statistics is divided into two types: [____] and non-parametric.
parametric
- 05
Which discipline establishes the theoretical foundations of statistical techniques?
Mathematical Statistics
- 06
In 1749, who introduced the German term Statistik to refer to the analysis of State data?
Gottfried Achenwall
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