1 Data processing and exporting Module 2 Session 6

2 Overview The next slide again shows the data management cycle. Data have been entered (and checked) in Epi Info. We are now ready to undertake data analysis. Do we remain in Epi Info, or move to another software? This session explores both: simple data analysis in Epi Info and exporting data – so that analysis can be undertaken in another software if required.

3 Design survey Design questionnaire Enumerators collect data in the field Data entered onto computer Manual checking, editing etc. Data analysis Reporting of results Computer data management Data management cycle Conception We are now ready to move on to the data analysis stage

4 Contents Using Epi Info to merge data from separate files Simple summaries, tables and graphs in Epi Info Exporting data from Epi Info to use with other programmes

5 Learning Objectives At the end of this session participants will be able to: merge data from separate data files use Epi-Info to produce tables, graphs and summary statistics and interpret the results export data from Epi Info for reading into another software package.

Merging Data There are three common types of merging: Top to Bottom – Adding records – Merge Side to Side – Adding variables – Relate Table Lookup – Data at different levels - Relate 6

Top to Bottom Merge Used when data files have the same variables but different records Used to combine data entered by different data entry staff For example: A enters records 1 to 10, B enters records 11 to 20 IDVar1Var2var IDVar1Var2var

Side to Side Merge Used when data files have same records but different variables Each file should have key field(s) to ensure correct merging For example: Person A enters Health data, Person B enters Education data IDHealth1Health IDEduc1Educ

Table Lookup Merge Used for data at different levels For example: Household data and data on individuals within the household Household ID must appear in Individuals dataset 9 HHIDWALLROOFFLOOR HHIDIDGENDERAGE

Activity 2 The first part of the practical takes you through the process of a side-to-side merge An example of the Table Lookup merge appears in Activity 4 The top-to-bottom merge is a much simpler and more intuitive process so is not included in this practical 10

Data Checking with Analysis Initial data analyses can be part of the data checking process Useful to check on spellings and ranges – e.g. are all ages feasible? Useful to have ability to produce simple tables and charts from the data entry package Corrections then made in the same package 11

12 Data Analysis in Epi Info The Analyze Data utility in Epi Info produces tables, graphs and summary statistics. The relevant commands are: Frequencies : 1-way tables Tables : cross-tabulations (2-way tables) Means: mean values Graph : graphs and charts Summarize: summary statistics

13 Frequencies (FREQ command) is used for 1-way tables

14 Tables is used for cross-tabulations

15 Means produces mean, median, minimum, maximum, quartiles, standard deviation.

Graph Offers a wide choice of graphs 16

Example Bar Chart 17

Labelling values When data have been entered as numeric codes the graphs do not give much information To label the value we first define a new text variable Then we recode the existing numeric variable into the new variable 18

Define and Recode 19

Revised Bar Chart 20

21 Activity 4 For your dataset, generate: Frequencies for the categorical variables Means for the continuous variables Cross-tabulations Graphs The results are copied to a Word file to be used in a report (sessions 10 & 11)

Moving out of Epi Info The Write (Export) command within Analyze Data exports data from Epi Info. 22

Options on the Export When exporting to Excel the options are Excel 3.0 or Excel 4.0 These are earlier versions of Excel – only one worksheet per file – but they can be read by the later versions of Excel You can choose which variables to export Note Epi-Info gives no indication that the export has been done – re-running the command will append the same data to the worksheet! 23

Variable and Value Labels Variable labels in Epi-Info are the prompts or questions Value labels can only be done by recoding into a different variable 24

Labels in Exported file In resulting Excel file variable names are used as column headings Text fields come across too 25

Vlookup Function in Excel Alternatively export only the numeric codes and use Vlookup in Excel for labels Codes are stored in a separate worksheet =vlookup(C2, Codes!$A$2:$B$8, 2, FALSE) Advantage is that codes are synchronised with labels 26

Vlookup Example 27

Activity 6 (Optional) Export some of the data you have been working on into Excel Try to use the vlookup function to label the coded variables For more information about the Vlookup function see Chapter 5 – Multi-level Data of SSC Introduction to data handling in Excel – SADC version 28