Data anaylsis_introduction Data_and_Statistics.pdf

This is a pdf that will help with data analysis and statistics

1. BIOSTATISTICS
PHR 211
Lecture 1

2. Chapter 1: Data and Statistics
◦Data
◦Data sources
◦Types of statistics
◦Nature of data
◦Levels of measurement

3. Definition
◦Thewordstatisticshastwomeanings.Inthemostcommonusage,statisticsrefersto
numericalfacts.Thesecondmeaningofstatisticsreferstothefieldordisciplineofstudy.
Inthissense,statisticsisagroupofmethodsusedtocollect,analyze,presentand
interpretdataandmakedecisions.

4. Why Do We Need Statistics?
◦The study of statistics has become more popular than ever over the past four
decades or so. The increasing availability of computers and statistical packages
has enlarged the role of statistics as a tool of empirical research.
◦Like almost all fields of study, statistics has two aspects: Theoretical and applied.
The former, also called mathematical statistics deals with the development of
theorems, formulas, rules, and laws. The latter involves the application of those
theorems, formulas, rules and laws. The main aim of this lecture is to introduce
statistics including the nature of data as well as the levels of measurement that
can be used.

5. Functions of Statistics
◦Statistics provides methods for:
◦Design: Planning and carrying out research studies.
◦Description: Summarizing and exploring data
◦Inference: Making predictions and generalizations about phenomena represented
by data.

6. Definitions
◦Dataare the facts and figures collected, summarized, analyzed, and interpreted.
◦The data collected in a particular study are referred to as the data set.
◦The elementsare the entities on which data are collected.
◦A variableis a characteristic of interest for the elements.
◦The set of measurements collected for a particular element is called an
observation.

8. In statistics, we commonly use these key terms:
◦Population is the complete collection of elements to be studied.
◦Sampleis a sub collection of elements drawn from a population.
◦Variables:numerical or categorical
◦Dataare the actual values of the variable. They may be numbers or words

9. Types of Statistics
◦Broadly speaking, statistics can be divided into two areas: descriptive
statistics and inferential statistics.
◦Descriptive statistics consists of methods for organizing, displaying
and describing data by using tables, graphs and summary methods.
◦Inferential statistics consists of methods that use sample results to
help make decisions or prediction about a population.

10. Data Sources
Existing Sources:
◦Within an organization –almost any department Database services –NCBI
◦Government agencies-Bangladesh Bureau of Statistics
◦Industry associations – Bangladesh Association of Pharmaceutical Industries
◦Special-interest organizations –Pharmacy Council of Bangladesh
◦Internet–more and more organizations/firms

11. Statistical Studies
◦In experimental studies the variable of interest is first identified. Then one or
more other variables are identified and controlled so that data can be obtained
about how they influence the variable of interest.
◦In observational (non-experimental)studies no attempt is made to control or
influence the variables of interest e.g. a survey

12. Nature of Data
Two types of data can be identified as qualitative and quantitative
data.
1.Qualitative datadeals with characteristics and descriptors that cannot be easily
measured.
◦It can be separated into different categories that are distinguished by some non-
numerical characteristics.
◦Qualitative data are the result of categorizing or describing attributes of a
population. Ethnic group, hair colour, blood type are all types of qualitative
data. They are generally described by words or letters.

13. Quantitativedata
Discretedata
(counts)
Continous data
(measurements)

14. 1.Quantitative data consist of number representing counts and
measurements.
◦Discrete data (counts) have finite values such as sex and race and can be
grouped into mutually exclusive categories.
◦For example, the number of students in class or the number of children in a
family ( you can’t have 2.5 children)
◦Continuous data (measurements)is quantitativedatathat can be
measured but not counted. It has an infinite number of possible values within
a selected range.
◦For example, age, height, weight are infinitely divisible and do not have
specific finite values.
◦The statistical test to apply to data depends on whether the variables are
discrete or continuous.

15. Levelsof measurementof data
Theway a setof datais measured iscalleditslevelof measurem ent.
Data canclassifiedintofourlevelsof measurem ent. Theyare:
1.Nominalscalelevel
2.Ordinalscalelevel
3.Intervalscalelevel
4.Ratioscalelevel

16. 1.Nominalscale level:
◦DatathatismeasuredusinganominalscaleisqualitativeItischaracterizedby
datathatconsistsofnames,labelsorcategories.Nominaldatacommonly
identifiesgroupsoftwomembers,e.g.maleorfemale,leftorright,youngor
old,yesorno,etc.Nominaldataarenotorderedandcannotbeusedin
calculations.
2.Ordinalscalelevel:
◦Thisscaleissimilartonominalscalebutitisdifferentasdatacanbeordered.
Forexample,whenresponsesareorderedfromthedesiredresponsestothe
leastdesiredone:excellent,good,satisfactory,unsatisfactory.
*Likethenominal scale,ordinalscaledatacannotbeused in calculations.

17. 3.The intervalscalelevel
◦Liketheordinal,with the additionalpropertythatmeaningfulamountsof
differences betweendatacan be determined.However,thereis no natural
zerostartingpoint. In otherwords,theintervalscalehas a definiteordering,
the differencebetweenintervalscaledatacan bemeasured, but thereis no
startingpoint.
Example :TemperaturescaleslikeCelsius(C) aremeasuredby usingthe
intervalscale. Inbothtemperatures,40 degreeis equalto100degreesminus
60 degrees.Differencesmake sense. pH is also an example of an interval scale.
*Zeroisnottheabsolutelowesttemperature.
*Thiskindof datacanbe usedincalculations.

18. 4.TheRatioscalelevel
◦Liketheintervallevelbut,inaddition,ithasa0pointandratioscanbe
calculated.Forexample,thefinalexamscoresare18,15,10and9(outof
20).Thisscalemustcontainazerovaluethatindicatesthatnothingexistsfor
thevariableatthezeropoint.
*Thedatacan beput inorder:9, 10, 15 an18
*Thedifferencebetweendata havemeaning:
◦thedifference between score18 and9 is 9 points.
◦Ratioscan be calculated:Thesmallestratioscoreis 0.
◦So,9 is twice18. The scoreof 18 is betterthanthescoreof 9.
Intervalandratiomeasurementlevelsarethemostdesirableaswecanusethe
morepowerfulstatisticalproceduresavailableformeansandstandarddeviations.