SADC Course in Statistics Introduction and Study Objectives (Session 01)

SADC Course in Statistics

Introduction and Study Objectives

(Session 01)

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Module Overview

• Sample to population inferences, e.g. estimating population characteristics

• Measuring the precision of such estimates• Concepts underlying hypotheses about

population parameters• Introduction to commonly used statistical

distributions• Basic tests for comparing means,

variances, proportions• Tests for association


Module aims

By the end of this module, you will be able to • explain basic concepts for making sample

to population inferences• calculate and interpret standard errors and

confidence intervals for simple problems• conduct statistical tests to compare two

means or two proportions• discuss the use and limitations of tests of

significance• have an appreciation of what is meant by a

non-parametric test


Aims – this session…

By the end of this session, you will be able to

• appreciate the different type of objectives that may arise in real life situations

• critically assess the type of information needed to address questions of interest

• recognise that real situations have complex data structures which have to be ignored in this module in order to understand the basic concepts better without distraction


Objectives related to estimation

To estimate• proportion of rural households that are food

insecure (<6 months food for family) in Zimbabwe

• average amount of land available for cultivation in Swaziland

• infant mortality rate, i.e. deaths per 1000 live births in Zambia

• total number of tobacco estates of <20 ha owned by small-holder farmers in Malawi


Objectives related to comparisons

Examples of questions of interest are:• is distance from school an impediment to

school enrolment amongst girls?• is there a difference in child-stunting

(measured by height-for-age standardised score<-2) between rural & urban areas

• is there evidence that agro-forestry farmers are more food secure (measured by no. of months food is available for family) than non-agro-forestry farmers?


Objectives related to relationships

Is there a relationship between

• diarrhoea episodes in a household and availability of access to clean water

• use of contraceptives and educational level of household head

• farmers’ adoption of soil fertility management methods and gender?

• use of mosquito nets and occurrence of malaria?


Initial data analysis requirements

Need first to identify• the ultimate sampling unit on which

measurements are to be made• actual measurements needed, plus clarity

on the calculation of any derived variable(s)

It will also be useful to think about• the type of data format (say as an Excel

spreadsheet) needed for the analysis

Some examples follow…


Initial steps – some examples

Example 1. Estimating the proportion of rural households that are food insecure in Zimbabwe

Unit: Household

Measurement: Number of months in past year when food was available for whole family

Derived variable: Coded as 0 if above measurement 6, 1 otherwise


An example with a hierarchy

Example 2. Estimating the average number of years of formal education in rural Zimbabwean households

Units (within HH): Household membersMeasurements: Years of education for each member in the household, and HH sizeDerived variable: Average number of years of education = Sum above measurements divided by HH size (needed since objective is at the HH level, measurement at person level)


What else is needed?What is the data format for above examples at the HH level?

Below is an illustration (showing fictitious values)

Given data in this format, can questions posed in Examples 1 and 2 be answered?


What about the actual data structure?

Above approach assumes there is no furtherstructure to the data. But there may be:

• further information at HH level, e.g. extent to which the HH relies on subsistence farming, number of employed persons in the HH, etc.

• information on how the HH’s were selected, e.g. purposively choosing predominantly rural districts, then smaller administrative units within districts, and finally HHs – this is a hierarchical structure


Recognising Limitations

Correct approaches to data analysis should allow for the data structure and the possible influence of other factors.

However, this module is only aimed at covering the basic statistical concepts.

So we will ignore the real complications in the remainder of this module in order to understand the basic concepts without distraction.


Practice and DiscussionFor the first 2 questions below, identify thestarting components necessary for ananalysis as illustrated in Examples 1 & 2. A joint discussion will follow regarding (c).

(a) What is the average amount of land available for cultivation amongst subsistence farmers?

(b) Is distance from school an impediment to school enrolment amongst girls?

(c) What is the relationship between use of bednets and occurrence of malaria?


Practical work follows to ensure learning objectives are

achieved…

SADC Course in Statistics Introduction and Study Objectives (Session 01)

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