د.ناهد الجميلي
Biostatistics
Statistics is a field of study concerned with collection, organization, summarization
and analysis of data.
Biostatistics is the application of statistics in medical research.
Terms in Biostatistics
• Data: – all the information we collect to answer the research question
A variable: It is a characteristic that takes on different values in different
persons, places, or things. For example: - heart rate, the heights of adult
males, the weights of preschool children, the ages of patients seen in a dental
clinic.
• Population: – is the entire group of individuals you want to study
• Sample: – a subset of the population for which data are collected
It is helpful to divide variables into different types; as different statistical methods
are applicable to each. The main division is into qualitative (or categorical) or
quantitative (or numerical variables).
Types of variables:
1- Quantitative variables:
It can be measured in the usual sense. For example: -
the heights and the weights.
2- Qualitative variables:
Many characteristics are not capable of being measured.
Some of them can be ordered (called ordinal) and Some of them can’t be ordered
(called nominal). For example: - classification of people into socioeconomic
groups, hair color
Types of quantitative variables:
1-Discrete variables: is characterized by gaps or interruptions in the values that it
can assume.e.g:
The number of daily admissions to a general hospital.
2- Continuous variables:
can assume any value within a specified relevant
interval of values assumed by the variable. For example: - Height, - weight, - skull
circumference. No matter how close together the observed heights of two
people, we can find another person whose height falls somewhere in between.
Types of qualitative variables:
1-Nominal:
As the name implies it consist of “naming” or classifies into various
mutually exclusive categories for example: - Male - female - Sick - well - Married –
single – divorced.
2-
Ordinal: Whenever qualitative observation Can be ranked or ordered
according to some criteria. For example: - Blood pressure (high-good-low) -
Grades (Excellent – V.good –good –fail). The spaces or intervals between the
categories are not necessarily equal.