Epidemiologist

Epidemiologist
Epidemiologists help with study design, collection and statistical analysis of data, and interpretation and dissemination of results (including peer review and occasional systematic review). Epidemiology has helped develop methodology used in clinical research, public health studies and, to a lesser extent, basic research in the biological sciences

Rabu, 06 November 2013

DATA INTERPRETATION AND USAGE

DATA INTERPRETATION AND USAGE

The data in this report is presented using maps that show the spatial distribution of indicator proportions over the survey area. Each is accompanied by a histogram that shows the distribution of estimates of indicator proportions in each of the sampled communities. Additional information is presented in tables for some indicators. Data from the qualitative plug-in is integrated into the text and presented in text boxes.
Presenting the data in map form allows the Periodic Review to identify areas of highest need and can be used to inform strategic programming decisions. The first round of the Periodic Review may also be seen as providing a baseline against which progress will be measured by examining changes in indicators between survey rounds.

WHAT IS AN INDICATOR?

For the purposes of the Periodic Review, an ‘indicator’ is a characteristic that varies across different people, households and communities being surveyed and which can be measured. Measurements may be collected by questionnaire survey or using simple and rapid techniques such as observation or physical measurement by surveyors.
Indicators are usually answers to simple yes / no questions. An indicator may be the answer to a single question or it may be derived from a set of answers to questions that are combined using logic of varying complexity. For example, the definition of the indicator for ‘exclusive breastfeeding’ used in the Periodic Review is derived from a combination of four variables: the age of the child; they are breastfed; they take solid or puréed food; and they take fluids other than breast milk.
These are combined using the following logic:
If the child is: aged six months or younger; the child is breastfed; and the child does not take solid or puréed food; and does not take fluids other than breast milk - then the child is ‘exclusively breastfed’.
The variables and logic used to create a definition of an indicator are called the criterion of the indicator. This is the characteristic that the indicator is intended to reflect. In some contexts, indicators may be associated with a standard that specifies a threshold.
For some indicators, the Periodic Review can be seen as a needs assessment, and for others a performance assessment.

WHAT IS SPATIAL SAMPLING?

The use of a grid sample means that communities surveyed are roughly the same distance apart. Spatial sampling was used because the assumption that the results for an indicator would be similar across the entire survey area (spatial homogeneity) was considered to be an unrealistic representation of the true situation.
The impact of a cyclone varies dramatically depending on the strength and duration of the storm in a particular location, whether areas were affected by high winds and/or the storm surge, as well as the geography of the area exposed to the storm. For the same reason, spatial sampling was used for the VTA. Spatial heterogeneity is also the reason why summary statistics for the entire survey sample are not presented, as these are often misleading when there is considerable spatial diversity.
The Periodic Review used a nearly even first-stage spatial sample to select communities and a representative second-stage sample to select households within the selected communities. This approach differs from population-based approaches that seek to give each person in the survey area an equal chance of being surveyed and thereby bias the distribution towards towns and more populated areas. By using a spatial sampling technique and a representative second stage sample, analysis across geographic areas can be used and presented in maps.

HOW DO I READ THE MAPS AND HISTOGRAMS?

Each indicator is mapped across the survey area and is presented in a figure that includes a map and a histogram. The colours on the map represent estimated proportions of households or, in some cases, individuals meeting the criteria associated with a given indicator which is given in the title of the map and explained in the associated text. The colours used on these maps are consistent with red always representing the poorest result and dark green representing the best result. A gradation of orange, light green and yellow represent values between the extremes of the collected data.
The legend at the bottom right of the map shows the highest and lowest of the indicator ranges. These are most often 0 and 100 per cent, but the range is restricted for some indicators (e.g. the incidence of global acute under nutrition).
Each map is accompanied by a histogram which shows the distribution of the estimated proportions of households or, in some cases, individuals meeting the criterion associated with a given indicator in each of the sampled communities. Additional graphs are provided for some indicators (e.g. reasons for non-attendance at school). These graphs present supplementary information that can assist in interpretation of the data.

WHAT IS IN THE TEXT BOXES?

The text boxes contain stories collected from the qualitative interviews with vulnerable households. They were selected to illustrate how the situation presented using maps and graphs is being experienced by individuals in the affected communities.
For each extract used, the full text from which it was selected is available in the Qualitative Results annex. The names of people and places given in this report are fictional and were changed to protect the anonymity of the interviewees.

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