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Session 1

Module Introduction and Getting Started with Stata

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Introduction

WelcomeHousekeeping Introductions

Name, job, district, team

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Module Overview

Module objectives are to provide you with

• Skills in data analysis

• Keeping in mind the analysis objectives

• While learning the use of a specialised statistical software package Stata

There will be a strong emphasis on conductingmeaningful analyses and on the interpretationof the results.

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Module content

Data management Data entry principles and practices

using Epi Info designing data capture screens, labelling and entering data, etc.

Simple statistical analysis in Epi Info and using the statistics package, Instat.

Report writing.

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Duration and timetable

Morning Afternoon

Day 1Getting started with Stata

Continued

Day 2 Tables Project work part 1

Day 3 Graphs Project work part 2

Day 4Reviewing inference: estimation and confidence intervals

Reviewing inference: Hypothesis testing

Day 5Tests of association in 2-way tables

Sampling weights

Day 6Project work part 3: writing the report

Putting it all in context

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Module Learning Objectives

At the end of the module, participants will :

appreciate the power of Stata as a statistical package be able to undertake elementary data management and

statistical analyses in Stata have updated their practical knowledge of the key statistical

inference concepts of estimation and hypothesis testing be able to produce graphs and tables using Stata, have sufficient knowledge of Stata to be able to work

independently to produce other analyses

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Prerequisites

Completion of Modules 1 and 2

At least a theoretical knowledge of statistical inference

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Resources

Stata software - version 10 This should be installed already It may need updating and a Stata “package”

adding – see later slides Guide to survey data analysis using Stata

Part 1 (Chapters 1 to 10) is used here Part 2 (Chapters 11 to 20) is supplied for

reference Inference guide

Used particularly in Sessions 7 and 8

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Concepts more than software

The emphasis is on the concepts of data analysis and statistical inference Using Stata

Rather than just on Stata itself Here we largely use the menus and dialogues Though ways of using and reading commands are

introduced Software is now easy to master

It is the statistical concepts that benefit from a course

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Learning objectives – sessions 1 and 2 These two sessions are about Stata Participants will be able to:

Load and save data Explore data

Using describe, codebook, summarize, etc Calculate new variables

Using generate, recode, etc Add labels to variables and to levels of a factor Create subsets of data using drop and keep

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Session Contents

In this session we look in particular at:

• Windows and menus in Stata

• Opening Stata data files

• Stata dialogues

• Typing and editing commands

• Using Stata as a calculator

• Exiting Stata

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The four Stata windows

Review

Stata Results

Variables

and window for typing Stata commands

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The Stata menus and toolbar

The three most important menus Data (for organising and managing the data), Graphics (for visual exploration & presentation), Statistics (for analysis).

Data, Graphics, Statistics

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Check Stata is up-to-date Use Help => Official updates

If updating is needed, either:

Do it automatically if you are connected to the internet

Or use the files on the CD/DVD that are under Stata resources

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The Data and Graphics Menus

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Your turn Click on several menus and explain their

usage to your neighbour You can deduce the menu from the logic of the task e.g. to draw a graph you go to the graphics menu!

Which menu would you probably need to use to: save data? sort a data set? produce a bar chart? tabulate the data?

Check by finding the dialogue in Stata

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Stata guide Section 1.2

You use Stata as a calculator Go through this section together Check the buttons at the bottom of the

dialogue They are the same on all dialogues

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Using Stata as a calculator

To perform calculations, use

Data Other utilities Hand calculator

Type 2+3 into the Expression slot

Press the Submit button

See answer in Results Window, and appearance of corresponding command in both the Results and Review windows.

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Results from the dialogue

You can get back to any dialogue box by typing db in front of the command name.

e.g. db display

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Creating an expression

Click create and then complete the resulting expression builder dialogue box.

Or type:display ln(10)

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Stata guide Section 1.3

From this point you use a dataset that is supplied Check that you have a working directory And that it has the files for this module

Copy them in, if not They are on the CD/DVD under Stata resources You could install the Stata package as well if you wish.

Then use Files => Change working directory To set this directory for the future

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Opening a Stata data file

Use the menu sequence File, Open…

select (highlight) the file named K_combined_short.dta

and click on Open

This will load the data from the Kenya socio-economic survey into Stata

Look at the Variables Window. What do you observe?

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Options within the Data menu

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An example of a dialogue box

Dialogue results from using the menu sequence

Data,

Describe data,

Describe data contents (codebook)

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In the codebook dialogue box…

The Submit button instructs Stata to execute the command, leaving the

dialogue box visible. The OK button does the same,

but closes the dialogue box. Cancel closes the dialogue box

without submitting the command to Stata. The R button resets the dialogue box

to its empty form. ‘?’ gives help on the command

associated with the dialogue box. The word “codebook” at the top of the dialogue

shows “codebook” is the command that will be generated

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Another dialogue box

Dialogue results from using the menu sequence

Data,

Describe data,

Summary statistics

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Results from codebook and summarize

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Your turn

In Chapter 1 of the Stata guide, go through

Section 1.3 Section 1.4 Section 1.5

Ask a resource person if you are unclear about

any parts of the above sections.

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Review

What do each of these buttons do?

Menus (and corresponding commands) used so far:•display•describe•codebook•list•generate•replace

•by/if//in

What does each one do?

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Your turn again

In Chapter 1 of the Stata guide, go through

Section 1.6 Section 1.7 Section 1.8

Ask a resource person if you are unclear about

any parts of the above sections.

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Review again

Explain to a neighbour why: (3<4) gives the value 1 in Stata (3>4) gives the value 0

They then explain to you why the expression: 1 + (age>24) + (age>60) Recodes a column into the values 1, 2 or 3

(Hint – see Section 1.6 Fig 1.19 and 1.20 if you need help)

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Typing and editing commands

Professional use of Stata for data analysis benefits by some use of Stata commands

These are typed into the Command Window To execute a command just press <Enter>.

To edit a previous command: Click on it in the review window, or use the Page-Up key – perhaps repeatedly.

In the Results Window A “dot” appears in front of executed commands whether generated by a dialogue, or by typing the

command.

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Command for listing data

In the command window, typing list region district household cluster

will show the contents of each of the variables region, district, household and cluster. (Note: Stata is case sensitive)

Pressing the GO button (see Stata menu bar) or the space bar allows you to scroll down the page

To stop the display, press the red break icon button or press the letter q on your keyboard.

To exit Stata, use:File Exit

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Your turn yet again

In Chapter 2 of the Stata guide, go through

Sections 2.1 and 2.2 (You can go further if you have time)

If you have your own data

And it is not already in a Stata file, then: In Chapter 3 of the Stata guide, go through

Sections 3.2.1, 3.2.2, 3.2.3 And discuss importing with the resource persons

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… and finally…

Consider a data set from your own district or ministry that is available as an Excel file.

Follow procedures similar to those in Section 3.2.3 of the Stata Guide, to load your Excel data set into Stata.

Save your data as a Stata file, giving it an appropriate name and noting the directory on your computer where it has been saved.

Note: You will return to this data set in sessions that follow.