Descriptive Stats
description
Transcript of Descriptive Stats
-
Descriptive Statistics and Inferential Statistics
-
AgendaData PreparationDescriptive StatisticsInferential Statistics
-
Data PreparationLogging the Data Checking the Data For AccuracyData Transformations
-
Descriptive StatisticsUnivariate Analysis Accesses properties of a single variableDistributionCenterSpreadCorrelation Shows ties between variables
-
Univariate Analysis (distribution)
-
Univariate Analysis (Center)Mean
Non-stable to extreme observationsVery useful in case of a normal distributionMedian
Great for visual comparison between distributionsVery useful in case of skewed distributionMode
Most frequent value in the distribution
-
Univariate Analysis (Spread)5 number summaryMin smallest observationQ1 median of the first half of a distributionMedian median of a distributionQ3 median of the second half of a distributionMax biggest observation
1.5 IQR rule
-
Univariate Analysis (Spread cont.)Standard DeviationShows relation of observations to the mean of a distributionCalculate a distance to mean for each valueSquare the results Divide a sum by the size of a distribution 1 (variance)Take a square root from variance
-
Univariate Analysis (Spread cont.)Standard DeviationEmpirical ruleapproximately 68% of the scores in the sample fall within one standard deviation of the mean approximately 95% of the scores in the sample fall within two standard deviations of the mean approximately 99% of the scores in the sample fall within three standard deviations of the mean
-
CorrelationNeed to determine whether there is a relationship between variables
-
Correlation (cont.)MagnitudeDirection
-
Correlation (cont.)Calculation
Test significance of produced valueSignificance levelDegree of freedom
-
Correlation (cont.)Situations when there is only 1 variable in the model are rare in real life. Need to compute correlation matrix.
-
Inferential StatisticsUsed for drawing conclusion about the population from a sampleEstimationEstimate true value of the parameter from a sampleHypothesis testingDetermine if there is a difference in a parameter value for two groups.
-
Inferential Statistics (General linear model )General linear model family of statistical models that produce most of inferential statistics
y = b0 + bx + e y outcomeb0 interceptx predictorsb coefficient estimatese error component
-
Inferential Statistics (General linear model cont.)Foundation for many statistical analysest-testChecks if means of two groups are different from each other on defined confidence levelANOVAChecks if there is a difference between more than two groupsANCOVAAdjusts the use of ANOVA by including covariates into the analysisRegression analysisCreates a model for predicting dependent variable
-
Inferential Statistics (Dummy variables.)Define different groups.
-
Research designExperimental Analysis. Quasi-Experimental Analysis.