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GAP Toolkit 5 Training in basic drug abuse data management and analysis. Training session 7 SPSS: Recode and Compute. Objectives. To introduce and demonstrate SPSS tools for recoding variables and creating new variables To introduce and demonstrate the use of SPSS command syntax - PowerPoint PPT Presentation
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GAP Toolkit 5 Training in basic drug abuse data management and analysis
Training session 7
SPSS: Recode and Compute
Objectives
• To introduce and demonstrate SPSS tools for recoding variables and creating new variables
• To introduce and demonstrate the use of SPSS command syntax
• To introduce and demonstrate Help features in SPSS from a dialogue box
Types of recode
• A categorical variable into a new set of categories• A continuous variable into a categorical variable
Example: pre-defined categories
• Recode weekly expenditure on drugs into the following categories:– Low expenditure <= £100 a week– High expenditure >= £101 a week
Frequency Percent Valid percent
Cumulative percent
Valid Low 31 62.0 62.0 62.0
High 19 38.0 38.0 100.0
Total 50 100.0 100.0
Weekly drug expenditure
Example: quantiles
• Recode weekly expenditure into the following:– 4 categories, each with approximately the same number of
cases (quartiles)– 10 categories, each with approximately the same number of
cases (deciles)
Frequency Percent Valid percent Cumulative percent
Valid <=£90 12 24.0 24.0 24.0
£91 <= X <= £98 12 24.0 24.0 48.0
£99 <= X <= £105 13 26.0 26.0 74.0
£106 <= X >= £116 13 26.0 26.0 100.0
Total 50 100.0 100.0
NTILES of Expend
Frequency Percentage Valid percentage Cumulative percentage
Valid 1 5 10.0 10.0 10.0
2 4 8.0 8.0 18.0
3 7 14.0 14.0 32.0
4 4 8.0 8.0 40.0
5 4 8.0 8.0 48.0
6 6 12.0 12.0 60.0
7 5 10.0 10.0 70.0
8 5 10.0 10.0 80.0
9 6 12.0 12.0 92.0
10 4 8.0 8.0 100.0
Total 50 100.0 100.0
NTILES of EXPEND
Compute
• Creates new variables using:– Standard mathematical operators– A full range of functions– Conditional statements
Explore: Yexpend
Statistic Std. error
Yearly drug expenditure Mean 5062.72 77.468
95% Confidence Interval for Mean
Lower Bound 4907.04
Upper Bound 5218.40
5% Trimmed Mean 5072.89
Median 5148.00
Variance 300062.3
Std. Deviation 547.779
Minimum 3848
Maximum 6032
Range 2184
Interquartile Range 754.00
Skewness -.333 .337
Kurtosis -.446 .662
Descriptives
Explore: Age
Statistic Std. error
AGE Mean 25.43 1.219
95% Confidence Interval for Mean
Lower Bound 22.97
Upper Bound 27.88
5% Trimmed Mean 25.21
Median 22.84
Variance 72.867
Std. Deviation 8.536
Minimum 11
Maximum 44
Range 32
Interquartile Range 12.77
Skewness .579 .340
Kurtosis -.518 .668
Descriptives
Help
• Context-sensitive Help:– Right click on any part of a dialogue box to obtain help
• Dialogue box Help button
Command language
• Command-line rather than Windows interface• More flexible• Reusable• Saved as text files
Syntax window
• Enter SPSS commands:– Type directly– Paste from a dialogue box
• Run SPSS commands• Save as a text file