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Data Analysis Using SPSS. SPSS-2. What is SPSS?. General Purpose Statistical Software Consists of three components Data Window - data entry and database (.sav) Output Window - all output from any SPSS session (.lst) Syntax Window - commands lines (.sps). SPSS-3. Data Entry & Preparation.
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Data Analysis Using SPSS
SPSS-2 What is SPSS? • General Purpose Statistical Software • Consists of three components • Data Window - data entry and database (.sav) • Output Window - all output from any SPSS session (.lst) • Syntax Window - commands lines (.sps)
SPSS-3 Data Entry & Preparation • Data entry New or Recalled (SPSS or non-SPSS) • Data Definition • Data Manipulation and Variable Development
SPSS-4 Data Definition • Purpose: Give meanings to the numbers for ease of reading the output • Involves • Data Format • Variable Name • Value Labels • Missing Values Command: Data Data Definition
SPSS-5 Data Manipulation • Recoding • To give new values to old values (especially reversing negatively worded questions) • To form nominal variable from continuous data • Variable Development • To form new variables combinations of old ones or functions of old ones • Command: Transform Recode/ Compute
SPSS-6 Data Analysis - Descriptive • Purpose: • To describe each variable - What is the current level of the variable of interest? • Command • Frequency • Means, Minimum, Maximum, Standard Deviation, Quartiles, Standard Deviation • Analyze Frequencies /Descriptives
SPSS-7 Data Analysis - Descriptive • Frequencies for two or more nominal variables • Analyze Summarize Crosstabulation • Means of variables by subgroups defined by one or more nominal variables • Analyze Compare Means Means (Use of Levels)
SPSS- 8 Parametric Test of Differences When • dependent continuous variable and we want to test differences across groups Command • Analyze Compare Means Independent t-test/ Paired t-test/ one-way ANOVA
SPSS- 9 Non-Parametric Test of Differences When • dependent variable ordinal or normal assumption not met Command • Analyze Non-parametric 2 Independent/ 2 related samples/ k independent samples/ k related samples
SPSS- 10 Parametric Two-Way ANOVA When • continuous dependent variable and related groups Command • Analyze General Linear Model Simple • Note: Fixed Factor Effect
SPSS- 11 Bivariate Relationship When • Covariation between two variables Correlation: • When both are continuous or ordinal Command Analyze Correlate Bivariate (with option for Spearman if both ordinal)
SPSS- 14 Regression Analysis When • To establish relationship between one continuous dependent variable and a number of continuous independent variables Command Analyze Regression Linear (Use Statistics, Save options) Issues: • Assumptions of Regression - normality; constant variance, independence of independent variables; independence of error terms
SPSS- 15 Regression Analysis Issues (cont.) • Outliers and Leverage Values • Choice of Selection Method of Independent Variables - Enter, Backward, Forward, Stepwise • Dummy Independent Variables Options • Residual Analysis; Influence Statistics, Collinearity Diagnostics, Normality Plots
SPSS- 16 Regression Analysis Interpretation • Goodness of Model: R2, F-statistics, Adj. R2, Standard error • Strength of Influence of Independent Variables: beta and standardized beta
SPSS- 17 Discriminant Analysis When • Dependent Variable is Nominal and the Purpose is to predict group membership on the basis of independent variables Command Analyze Classify Discriminant (Option: Classify by summary tables; Select - for holdout and analysis samples Issues • Similar to Regression
SPSS- 18 Discriminant Analysis Interpretation • Goodness of Analysis: Hits Ratio - compared to maximum chance, proportional chance and Press Q. • Univariate Results: To establish the discriminating variables
SPSS- 13 Factor Analysis When • To reduce the number of variables to underlying dimensions Command Analyze Data Reduction Factor (Option: rotation, save factor scores) Issues • Assumptions sufficient correlations between the variables (Bartlett test; anti-image, KMO test of sufficiency)
SPSS- 12 Reliability Analysis When • Before forming composite index to a variable from a number of items Command Analyze Scale Reliability Analysis (with option for Descriptives item, scale, scale if item deleted) Interpretation • alpha value greater than 0.7 is good; more than 0.5 is acceptable; delete some items if necessary