# Data analysis: frequencies GAP Toolkit 5 Training in basic drug abuse data management and analysis Training session 8.

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Data analysis: frequencies GAP Toolkit 5 Training in basic drug abuse data management and analysis Training session 8

Objectives Introduce univariate, descriptive statistics as the first step in a process of data analysis, starting from exploration and moving towards more sophisticated techniques Distinguish between frequencies and relative frequencies Introduce frequency and probability distributions as data models

Descriptive Statistics Univariate Categorical data Continuous data

SPSS Descriptive Statistics Analyse/Descriptive Statistics/Frequencies Analyse/Descriptive Statistics/Explore Analyse/Descriptive Statistics/Descriptives

Frequency vs relative frequency The frequency of any value of a variable is the number of times that value occurs in the data; that is, a frequency is a count. The relative frequency of any value is the proportion or fraction or percent of all observations that have that value. (D. S. Moore, Statistics: Concepts and Controversies, 5th ed. (New York, W. H. Freeman Press, 2000)).

Frequency distribution/probability distribution Frequency distribution: all possible values of the variable and their associated counts Probability distribution: all possible values of the variable and their associated probabilities (relative frequencies)

Percentages Let: –f 1 = the number of cases in category 1 –n = the total number of cases The percentage of cases in category 1:

Exercise: frequency of referral Construct a frequency table for referral source in the file main.sav

FrequencyPercentValid PercentCumulative Percent ValidSelf/Fam/Friends58637.338.0 Employer19512.412.750.7 Health Pro19412.312.663.3 Religious Grp654.14.267.5 Hosp/Clinic533.4 70.9 Welfare25216.016.487.3 Courts/Corrections1006.46.593.8 School644.14.297.9 Unknown322.02.1100.0 Total154198.1100.0 MissingSystem301.9 Total1571100.0 Referral

Frequencies: Format button

FrequencyPercentValid PercentCumulative Percent ValidSelf/fam/friends58637.338.0 Welfare25216.016.454.4 Employer19512.412.767.0 Health pro19412.312.679.6 Courts/corrections1006.46.586.1 Religious grp654.14.290.3 School644.14.294.5 Hosp/clinic533.4 97.9 Unknown322.02.1100.0 Total154198.1100.0 MissingSystem301.9 Total1571100.0 Referral

Frequencies: Charts button

Frequencies: Statistics button

Referral NValid1541 Missing30 Mode1 Statistics

Frequencies: syntax FREQUENCIES VARIABLES=refsourc /FORMAT=DFREQ /STATISTICS=MODE /BARCHART PERCENT /ORDER=ANALYSIS.

Exercise: frequencies Generate a frequency table and bar chart for each of the following variables and comment: –Race –Education –Employment Save the output and the syntax file

Frequency: Race FrequencyPercentValid PercentCumulative Percent ValidColoured72246.052.8 White52033.138.090.8 African1096.98.098.8 Asian171.11.2100.0 Total136887.1100.0 MissingSystem20312.9 Total1571100.0 Race

Frequency: Education FrequencyPercentValid PercentCumulative Percent ValidSecondary97862.364.3 Primary33221.121.886.2 Tertiary18912.012.498.6 None/pre-primary211.31.4100.0 Total152096.8100.0 MissingSystem513.2 Total1571100.0 Education

Frequency: Employment FrequencyPercentValid PercentCumulative Percent ValidWorking full-time57136.336.6 Not working56936.236.473.0 Student/pupil24015.315.488.3 Working part-time684.34.492.7 Pensioner342.2 94.9 Disabled332.1 97.0 Housewife281.8 98.8 Other181.11.299.9 Apprentice1.1 100.0 Total156299.4100.0 MissingSystem9.6 Total1571100.0 Employment

Summary Frequencies and relative frequencies Frequency distributions and probability distributions Format/ordering Bar charts Statistics/mode

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