Sociology: Social Networks, Social Support

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Biostatistics
College of Medicine University of Malawi

2011

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Learning Objectives
By the end of this lesson you should be able Explain importance of Biostatistics Distinguish between types of variables Explain different types of measurement scales

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Definition of Statistics

Statistics is the science that studies the collection and interpretation of numerical data. Field of statistics is divided into Mathematical and Applied statistics.

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Applied statistics concerns the application of the methods of mathematical statistics to specific areas such as public health, economics etc Biostatistics is the branch of applied statistics that concerns the application of statistical methods to medical and biological problems

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Importance of Biostatistics
To better understand reports of research studies in your field To obtain a foundation in statistical issues for designing and conducting your own research. To learn a few techniques for analyzing data

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Variables, Measurement Scales and Summarizing data

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Definition of a Variable
A variable is a characteristic that can have many different values.

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Types of Variables
A categorical variable has values with interruptions or gaps between them (categories) A continuous variable has values that could, theoretically, be measured without gaps

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Scales of Measurement
Qualitative
Nominal Ordinal Binary

Quantitative
Discrete Continuous

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Qualitative

Consists of a finite set of possible values or categories Always categorical

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Nominal scale
Qualitative categories which have no particular order. Examples:

Diagnosis
Malaria AIDS Accident Other
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Ethnic group
Chewa Yao Tumbuka
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Binary scale
Two qualitative categories Examples: Gender
Male Female

HIV status
Uninfected Infected

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Ordinal Scale
Qualitative categories that have a natural order. As a result, we can decide that one outcome is "less-than" or "more-than" another.

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Examples:
View of statement that condoms can help prevent spread of AIDS Agree No opinion Disagree

Severity of diarrhea
None Mild Moderate Severe

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Quantitative
Numerical measurements or counts May be categorical or continuous

Discrete Continuous

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Discrete scale
There are a limited number of distinct possible values or group of values Examples: Number of children in a family Number of decayed, missing or filled teeth 2011 16

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Continuous
Numeric scale with infinitely many values between any two observed values. Examples: Weight in kg Age 2011 17

Summary
Qualitative Quantitative

Categorical

Nominal Ordinal Binary

Discrete

Continuous

Continuous

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Understanding the scale of measurement of data is key to knowing the correct methods for summarizing data graphical display of data analysis of data.

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