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Data processing and exporting

Module 2 Session 6

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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.

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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

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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

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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

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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

ID Var1 Var2 var3

01 24 54 62

02 32 54 14

03 54 24 35

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ID Var1 Var2 var3

04 35 45 12

05 64 74 25

06 54 54 65

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

ID Health1 Health2

01 02 03

02 04 05

03 14 24

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ID Educ1 Educ2

01 34 45

02 71 55

03 62 34

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

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HHID WALL ROOF FLOOR

10001 02 03 01

10002 03 03 01

10003 04 05 01

HHID ID GENDER AGE

10001 01 01 51

10001 02 02 48

10001 03 01 20

10002 01 02 84

10003 01 01 56

10003 02 02 51

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

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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

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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

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

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Tables is used for cross-tabulations

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Means produces mean, median, minimum,

maximum, quartiles, standard deviation.

Graph Offers a wide choice of graphs

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Example Bar Chart

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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

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Define and Recode

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Revised Bar Chart

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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.

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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!

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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

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Labels in Exported file

In resulting Excel file variable names are used as column headings

Text fields come across too

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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

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Vlookup Example

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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

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