GAP%20Toolkit%205%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20%20Training%20in%20basic%20drug%20abuse%20data%20management%20and%20analysis

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GAP Toolkit 5
Training in basic drug abuse data
management and analysis
Training session 7 SPSS Recode and Compute
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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

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Types of recode

• A categorical variable into a new set of
  categories
• A continuous variable into a categorical variable

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Recode approaches

• Into pre-defined categories of interest
• Into categories of equal size

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Example pre-defined categories

• Recode weekly expenditure on drugs into the
  following categories
• Low expenditure lt 100 a week
• High expenditure gt 101 a week

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select variable for recoding and click
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click here to map old ? new values
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Weekly drug expenditure
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
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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)

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NTILES of Expend
Frequency Percent Valid percent Cumulative percent
Valid lt90 12 24.0 24.0 24.0
91 lt X lt 98 12 24.0 24.0 48.0
99 lt X lt 105 13 26.0 26.0 74.0
106 lt X gt 116 13 26.0 26.0 100.0
Total 50 100.0 100.0
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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
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Compute

• Creates new variables using
• Standard mathematical operators
• A full range of functions
• Conditional statements

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Transform/Compute
click here to define variable type
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Type and Label
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YexpendExpend52
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Explore Yexpend
Descriptives
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
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Example 2 Age

• Convert date of birth to age in years

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(DATE.DMY(01,01,2002) - dob) / (365.25246060)
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Explore Age
Descriptives
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
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Help

• Context-sensitive Help
• Right click on any part of a dialogue box to
  obtain help
• Dialogue box Help button

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Command language

• Command-line rather than Windows interface
• More flexible
• Reusable
• Saved as text files

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Syntax window

• Enter SPSS commands
• Type directly
• Paste from a dialogue box
• Run SPSS commands
• Save as a text file

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The Paste button
click to copy command into Syntax Window
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The Run menu
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Syntax for Age
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Summary

• Recode
• Into same variable
• Into different variable
• Compute
• Mathematical operators
• Functions

• Dialogue box Help
• Context-sensitive Help
• Dialogue box Help button
• Command language
• Syntax Window
• Dialogue box Paste button