1 stat.ppt

Lectures of Stat -145
(Biostatistics)
Text book:
Biostatistics
Basic Concepts and Methodology for the Health
Sciences
By
Wayne W. Daniel
Prepared By:
Sana A. Abunasrah
Revision By:
Saba M. Alwan

Text Book : Basic Concepts and
Methodology for the Health Sciences
2

3
• Key words :
– Statistics , data , Biostatistics,
– Variable ,Population ,Sample

4
Statistics is a field of study concerned with
1- collection, organization, summarization and
analysis of data.
2- drawing of inferences about a body of data
when only a part of the data is observed.
Statisticians try to interpret and
communicate the results to others.

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* Biostatistics:
The tools of statistics are employed in many fields:
business, education, psychology, agriculture,
economics, … etc.
When the data analyzed are derived from the
biological science and medicine,
we use the term biostatistics to distinguish this
particular application of statistical tools and
concepts.

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• The raw material of Statistics is data.
• We may define data as figures. Figures result
from the process of counting or from taking a
measurement.
• For example:
• - When a hospital administrator counts the
number of patients (counting).
• - When a nurse weighs a patient
(measurement)

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We search for suitable data to serve as the raw
material for our investigation.
Such data are available from one or more of the
following sources:
1- Routinely kept records.
For example:
- Hospital medical records contain immense
amounts of information on patients.
- Hospital accounting records contain a wealth
of data on the facility’s business activities.

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2- External sources.
The data needed to answer a question may
already exist in the form of
published reports, commercially available
data banks, or the research literature, i.e.
someone else has already asked the same
question.

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3- Surveys:
The source may be a survey, if the data
needed is about answering certain
questions.
For example:
If the administrator of a clinic wishes to
obtain information regarding the mode of
transportation used by patients to visit the
clinic, then a survey may be conducted
among patients to obtain this information.

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4- Experiments.
Frequently the data needed to answer a
question are available only as the result of an
experiment.
For example:
If a nurse wishes to know which of several
strategies is best for maximizing patient
compliance, she might conduct an experiment in
which the different strategies of motivating
compliance are tried with different patients.

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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.

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Quantitative Variables
It can be measured in the
usual sense.
For example:
- the heights of adult
males,
- the weights of preschool
children,
- the ages of patients
seen in a
- dental clinic.
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
socio-economic groups
- hair color
Types of variables
Quantitative Qualitative

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A discrete variable
is characterized by gaps or
interruptions in the values
that it can assume.
For example:
- The number of daily
admissions to a general
hospital,
- The number of decayed,
missing or filled teeth per
child in an elementary
school.
A continuous variable
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 quantitative variables
Discrete Continuous

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As the name implies it
consist of “naming” or
classifies into various
mutually exclusive
categories
For example:
- Male - female
- Sick - well
- Married – single - divorced
.Whenever qualitative
observation
Can be ranked or ordered
according to some
criterion.
For example:
- Blood pressure
(high-good-low)
- Grades (Excellent – V.good –
good –fail)
Types of qualitative variables
Nominal Ordinal

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It is the largest collection of values of a
random variable for which we have an
interest at a particular time.
For example:
The weights of all the children enrolled in a
certain elementary school.
Populations may be finite or infinite.

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A sample is a part of a population.
For example:
The weights of only a fraction of these
children.

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• Question (6) – Page 17
• Question (7) – Page 17
“ Situation A , Situation B “

Q6: For each of the following variables
indicate whether it is quantitative or
qualitative variable:
(a) Class standing of the members of this
class relative to each other.
Qualitative ordinal
(b) Admitting diagnoses of patients admitted
to a mental health clinic.
Qualitative nominal
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(c) Weights of babies born in a hospital
during a year. Quantitative continues
(d) Gender of babies born in a hospital during a
year. Qualitative nominal
(e) Range of motion of elbow joint of students
enrolled in a university health sciences
curriculum.
Quantitative continues
(f) Under-arm temperature of day-old infants
born in a hospital.
Quantitative continues
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Q7: For each of the following situations,
answer questions a through d:
(a) What is the population?
(b) What is the sample in the study?
(c) What is the variable of interest?
(d) What is the type of the variable?
Situation A: A study of 300 households in a small
southern town revealed that 20 percent had at
least one school-age child present.
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(a) Population:
All households in a small southern town.
(b) Sample:
300 households in a small southern town.
(c) Variable:
Does households had at least one school age
child present.
(d) Variable Type
is qualitative nominal.
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• Situation B: A study of 250 patients admitted
to a hospital during the past year revealed
that, on the average, the patients lived 15
miles from the hospital.
(a)Population:
All patients admitted to a hospital during the
past year.
(b) Sample:
250 patients admitted to a hospital
during the past year.
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(c) Variable:
Distance the hospital live away from the
hospital
(D)Variable Type:
is Quantitative continuous.
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