Definitions●Measurement Unit The scale of the measurement variable●Measurement Variable The type of data you are collecting●Observation UnitThe unit you collect data from●Population of InterestThe population that youhopeto draw a conclusionabout●SampleThe collection of all sampling units that were selected●Statistical PopulationThe collection of all sampling units thatcouldbeselected to be in your sample●Sampling UnitThe unit that is selected at random●Descriptive statisticsis the set of tools used to describes the data in yoursample. This includes calculating quantitative descriptions (e.g., averagevalues) and creating graphs●Inferential statisticsis the set of tools used to say something about thestatistical population based on your sample. This includes things likeconfidence intervals and statistical tests.●Countsare used for categorical variables and are the number ofobservations in your sample that fall into each category.●Interquartile rangeuses quartiles to describe dispersion in anumerical variable. It is the difference between the 3rdand 1stquartiles and gives the range of the innermost 50% of a numericalsample.●Meanis the average value in your sample.●Median is the middle value of your sample when the values areranked from lowest to highest.●Proportions are used for categorical variables and are the share ofobservations in your sample that fall into each category●Quartileis one quarter of your sample when the values are rankedfrom lowest to highest. ●Rangeis the difference between the maximum and minimum valuesfor numerical variables, or the difference between the maximum andminimum number of counts for categorical variables.●Standard deviation is the square root of the variance
●Variance is the typical squared distance of the numerical values fromthe mean.●Categorical variablesare ones with qualitative levels●Continuous numericalvariables are numerical variables where thenumber can be something other than an integer●Data is a particular value of the variable●Discrete numerical variablesare numerical variables where thenumber can only be an integer●Nominal categorical variables are categorical variables that haveunordered levels●Numerical variablesare ones with numeric levels●Ordinal categoricalvariables are categorical variables that haveordered levels●Variableis any measurable characteristic of an observation unit. Theparticular value of a variable for an observation unit is the datum.●Difference calculations of effect size are Y1-Y2where Y1and Y2arethe means of samples from group 1 and group 2 respectively. ●Effect sizeis the change in mean value of the response variableamong groups.