COL NAILA AZAM

BiostatisticsINTRODUCTION

LEARNING OBJECTIVES

To understand the RELATIONSHIP OF BIO STATISTICS TO PUBLIC HEALTH

To correlate collection of data to basic requirement of VITAL STATISITCS

To clarify THE TYPES OF DATA collected during research

What Is Public Health?

“Public Health is the science and art of preventing disease, prolonging life and promoting health through the organized efforts of society.”

(World Health Organization)

The Functions of Public Health

Assessment: Identify problems related to the public’s health, and measure their extent

Policy Setting: Prioritize problems, find possible solutions, set regulations to achieve change, and predict effect on the population

Assurance: Provide services as determined by policy, and monitor compliance

Evaluation is a theme that cuts across all these functions, i.e., how well are they performed?

What is Biostatistics?

Statistics is the art and science of making decisions in the face of uncertainty

Biostatistics is statistics as applied to the life and health sciences

The press frequently quotes scientific articles about:

Diet The Environment Medical care, etc.

Effects are often small and vary greatly from person to person

We need to be familiar with statistics to understand and evaluate conflicting claims

VITAL STATISTICS

A branch of statistics that deals with the changes and most basic events of human populations: e.g., natality (birth); mortality (death); morbidity (illness and disease); injuries; marriage . . .

Vital statistics are indispensable in studying social and health trends, and making important legislative, commercial (marketing) and health decisions

Statistics are gathered from census and registrars’ reports, physicians’ records, medical examiners’/mosque records, grave yards, and a variety of other health professionals

RATES: DENOMINATORSAND NUMERATORS

Rates or ratios are used to measure most health problems

They consist of numerators and denominators: a count of events divided by the number of possible events

Numerators and denominators used in public health statistics are of three types: Survival data (births, deaths, and a count of the

population Health and socioeconomic status data Data based on health resources and utilization

THE DENOMINATORS

The most important information on which activities in public health must be predicated is a count of the population to be served

The decennial census is an important and the most widely used information as the denominator(defacto/dejure) May include intercensal estimates, based on projects or sample

surveys

Other sources of information may also be used, depending on the phenomenon of interest; for example -- School enrollment records Employer records of numbers of workers

THE DENOMINATOR

Airline carriers for numbers of passengers carried during a given time

Numerator data stem from administrative registration and reporting procedures

Most significant of activities relate to the vital events of birth, mortality (death), and morbidity (disease, illness, and injury

TYPES OF DATA

Just as we must classify and organize information before we can retrieve and use it ,

We must classify data into the correct type before we can do any statistical analysis on them.

WHY?

The data type will determine : How data can be coded for analysis? What kind of analysis can be performed?

CATEGORICAL DATA

Nominal data: variables are divided into a number of named categories without any intrinsic order Sex, marital status

Ordinal data: variables divided into number of ordered categories Level of knowledge, opinion on a statement

NUMERICAL DATA( expressed in numbers):possible values take a distinct series of numbersDiscrete continuous

NUMERICAL DATA EXAMINED THROUGH

Frequency distributionPercentages, proportions, ratios, rates FiguresMeasures of central tendencyMeasures of dispersion

EXAMPLES

1. while checking accuracy of clinical diagnosis of malaria, data frequency distribution of 33 slides is, Negative-19 P. falciparum-13 P.vivax-1

DATA ?? NOMINAL

2. 148 students were asked about attacks of palpitation on a scale:1/2=rare; 3/5= occasional; > 5 =frequent

Never=47Rare=71Occasional =24Frequent =6

DATA?????ORDINAL

FREQUENCY DISTRIBUTION OF NUMERICAL DATA

(GROUPING OF DATA)

Select groups for grouping the dataCount the number of measurements in each

groupAdd up and check the resultsGROUPING RULES:

Groups must not overlap No gaps (continuity in groups) Groups range from lowest to highest measurement;

round numbers for lower values) Equal width for copmarability

VARIABLES

A variable is a characteristic of a person,object,or phenomenon that can take on any or different values Age in years,months,weeks Weight in Kg ,pounds,stones,mg Distance in m, km , walking minutes Monthly income

Dependent , independent, confounding variables

The variable used to describe or measure the problem under study DEPENDENT VARIABLE

The variables used to describe or measure the factors that are assumed to cause or at least to influence the problem INDEPENDENT VARIABLE

Variable related to both above variables CONFOUNDING VARIABLE

EXAMPLE

CAUSE EFFECT (independent variable) - dependent variable

OTHER FACTORS Confounding variable

QUESTIONNAIRE

1. gender male------ female-------2. postal code of your home address-----3. how will you rate the quality of your

mobile service provider? Poor, fair, average, good, excellent

4. how many points have you accumulated for the bonus program?

5. how many SMS did you send yesterday?

6. how old are you?7. what is your yearly income?

<40000, [40-49.9], [50-59.9], [60- 69.9],[70-79.9], > 80000

NOMINAL DATA

The answer to Q 1 will be either male or female, but before analyzing the data ,we must code them by symbolically assigning a number to each possible answer. As 1 for female, 2 for male. Allowing limited calculations, no averages, only FREQUENCY COUNTED.

POSTAL CODE ?

To find residential location, again postal codes are labeled with numbers

No meaningful calculations allowed ; only simple counting.

So nominal data again

ORDINAL DATA

The 3rd question asks to rate the quality of service on a 5 point scale, the we can code the answers as 1 for poor and 5 for excellent(we can reverse the coding if we want)

The coding is not arbitrary,i.e 1 for poor and 5 for excellent by compulsion

We must only follow an order, from high to low or low to high

Indicating rank of inherent quality(4 better than 3, 5 more than 4)

Still we cant say

Difference between 1 & 2 is equal to difference between 3&4.

Numbers indicate only show order(better /worse), not how much better

Analysis of such data will again be restricted to frequency estimation only

Q NO. 4 introduces INTERVAL DATA

A more familiar example would be that of temperature scales of CELSIUS AND FARENHEIT (WHERE THERE IS NO ANSOLUTE ZERO, ZERO POINT IS arbitrarily chosen and an object at zero is not without heat. [an object at 32 degree F is at zero degree C.

An object at 20 degree is 5 degree less than one at 25 degree but we cant say that 20 degree is twice as warm as 10 degree.

INTERVAL DATA

Interval data has no absolute ZERO point

So we cant use comparisons as to twice as much or half as many with interval data.

Q NO 4 , of BONUS POINTS

The svc provider gives 2000 points to each user and then 100 points for each SMS . Users can claim various prizes on the basis of points collected.

As absolute zero is missing; earning 10000 points is not twice as much as earning 5000 points 10000- 2000= 8000 5000-2000=3000

IN Q NO 5 &6 --RATIO DATA

The answer to both questions is HOW MUCH GREATER OR LESSER.

There is an absolute zero point so zero SMS means no SMS

RATIO DATA

Provide information detailed information on HOW MUCH GREATER OR LESSER WE can USE COMPARISONS AS TO ‘TWICE AS

MANY ‘ with confidence and surety.

DATA CONVERSION

What about Q no 7??? With absolute zero / no income at all????? Are the incomes to be treated as ratio data????? Are these interval data ???????????

HOW ????

Respondents are asked to place themselves in one of the six categories from 1-6 with 1 as lowest and 6 as highest.

If you are in 4th cat and your friend in 2nd cat , then your income is higher than him/her

Again we cannot say how much? So we are collecting ORDINAL DATA

ANY QUESTIONS?????FEELING READY FOR RESEARCH

PROJECT??????