STATISTICAL METHODS STAT 303
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This 1 page Class Notes was uploaded by Celestino Bergnaum on Wednesday October 21, 2015. The Class Notes belongs to STAT 303 at Texas A&M University taught by J. Carroll in Fall. Since its upload, it has received 37 views. For similar materials see /class/225745/stat-303-texas-a-m-university in Statistics at Texas A&M University.
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Date Created: 10/21/15
Vocabulary Statistics A collection of procedures and principles for gathering data and analyzing information in order to help people make decisions when faced with uncertainty Data A plural word referring to numbers or nonnumerical labels collected from a set of entities Population The entire collection of individuals or measurements about which information is desired Sample A subset of the population selected for study Takes less time and money but we no longer know everything exactly we have some error Data set A collection of observations on one or more variables Distribution A pattern of variation of a variable Can be mathematical or graphical Variable a characteristic which changes when from observation to observation in a population Categorical Qualitative Variable A variable whose values cannot be interpreted as numbers With categorical data we can replace numbers with letters symbols etc Note When analyzing categorical data we will typically work with counts or percentages of objects Numerical Quantitative Variable Measurements or counts values which have meanings as numbers Discrete If the set of all possible values when pictured on the number line consists only of isolated points The most common type of discrete variable we will encounter is a counting variable Continuous If the set of all values when pictured on the number line consists of intervals Census Look at every object or individual in the population We know everything exactly but it takes a lot of time and money may even be 39 l quot 39 to do if are 39 39 eg average lightbulb lifetime Sampling Variability The differences between samples from the same population Random Sample A subset of the population selected so that every individual has a speci ed probability of being part of the sample Simple Random Sample A random subset of size n from a population where the subset is chosen in such a way that every possible subset of size n has the same chance of being selected as any other Sample Survey A method of gathering opinions and information from each individual included in the sample Possible problems nonresponse bias and volunteer sample both cause a nonrepresentative sample Observational Study Characteristics of the participants in the sample are observed Case Control Study A study in which cases having a particular condition are compared to controls who do not The idea is to compare them to see how they differ on the variable of interest Experiment A planned study in which the researcher collects data under different experimental conditions The researcher controls one or more variables and measures the effect of changes in that variable on some outcome of interest Randomized Experiment A study in which the treatments are randomly assigned to participants This may allow the researcher to determine cause and e ect Statistically Signi cant A relationship or difference that is large enough to be unlikely to have occurred in the sample if there is no relationship or difference in the population