How to prepare a thesis

GUIDELINES FOR PREPARATION OF DISSERTATION/THESIS

Dr. Gopalrao Jogdand, M.D. PhD. (U.S.A.)Professor & Head, Department of Community Medicine.

Dissertation

Why a dissertation? Just for fulfilling the requirement for

a doctoral degree program. For learning how to conduct medical

research scientifically. Basic requirement for starting career

as a researcher.

Types of research

Quantitative research: Aim is to measure certain variables. Estimation of population parameters. Statistical testing of hypothesis. Qualitative research: Mainly concerned with obtaining information

about certain population characteristics such as socio- economic status, concepts about health, health seeking behaviour, utilization of health services.

Selecting a research topic After rigorous scanning of medical

literature, studying relevant material from the internet or guidance from the guide/Supervisor.

A blue print of the research topic is formed in the mind of a postgraduate student.

This idea can be further crystallized by collecting references from various sources.

Avoid duplication or collection of trash references.

Planning

Administrative feasibility: Check for available research facilities in your institution or the collaborating agency.

Procure administrative clearance from the ethical committee.

Procure permission from the agency where the study has to be conducted.

Procure Informed consent of study participants/patients.

Operational feasibility in field based research studies/community based studies assess the participation and co-operation of the study population and the resources required.

Financial feasibility.

Scanning the medical literature

Collection and review of relevant literature.

Searching for cumulative index medicus in the library.

Index medicus is available in two forms:

a. Author index. b. Subject index. Collecting references from National

and International journals.

Resources on the net

List of some Important Internet websites:- 1. http://www.isoc.net 2. http://www.medlineplus.gov 3. http://www.clinicaltrials.gov 4. http://www.hon.ch 5. http://www.nlm.nih.gov 6. http://www.biosis.org 7. http://www.sis.nim.nih.gov 8. http://www.healthnet.org.za 9. http://www.pubmedcentral.nih.gov 10. http://www.reliefweb.int 11. http://www.nic.in 12. http://www.pubmed.com

Selection of a study design This will depend on the research

question and the best possible way to address it.

Descriptive studies: 1. Case report and case series. 2. correlation studies. Observational studies 3. cross-sectional surveys.

Analytical studies: 1. case control studies.

2. Cohort studies. 3. Experimental studies.

Preparation of a study protocol

Research question. Rationale and apriori hypothesis on the study. Review of literature. Aims and objectives. Preparation and validation of questionnaire, by

pilot study. Material and methods. Summarization of data and statistical analysis. Appendices. Summary. Bibliography.

Sampling strategies

Why sample size? For addressing the research question

scientifically and for avoiding certain biases and fallacies.

Chance bias. Statistical fallacies.

Basic concepts

Population:

Universe:

Reference populn:

Parent Population:

A group of individuals in which the researcher is interested

The Process or Technique of selecting a sample of appropriate characteristics and adequate size

Sample: Subset of the population

Sampling Frame: Total elements of the survey population, redefined according to certain specifications

Parameters: Summary Measures e.g. Averages; Percentages.

Sample Statistics: Summary measures of sample

Sampling error:

The difference between population parameter and sample statistics

Basic Requirements of a Reliable Sample

‡ Efficiency: ability to yield desired information

‡ Representativeness: Similarity to reference population.

‡ Measurability:valid estimates of variability

‡ Size:adequacy

‡ Coverage:inclusion

‡ Goal Orientation:oriented to research design,

objectives

Sampling Procedures

‡ Non-probability Samples:

# Incidental

# Quota

# Purposive

‡ Multi Phase Sampling:

‡ Sequential Sampling (Quality control):

‡ Panel Sampling:

Probability Samples

Ø All members have equal chance of selection

Ø List all members of population

Ø Random selection: Dice, Coins, Lottery, pages of book

Random tables, calculator,

computer

Random Sampling

Ø Stratification of area through maps

Ø Random selection: Dice, Coins, Lottery, pages of book

Random tables, calculator,

computer

Systematic Sampling

Ø First is chosen randomly

Ø Others are chosen systematically

Area Sampling

Ø Enumeration of sampling Units

Ø Cumulative counting.

Ø Random selection: First Cluster unit selection

Ø Each cluster 7 units selection by random.

Ø Total 30 clusters. A total of 210 units

Ø Most commonly used method

Cluster Sampling

Ø Collect basic data from large sample

Ø Collect details from sub sample.

Multiphase Sampling

Ø First select small sample

Ø If questions are not answered, increase the sample size.

Ø Quality control methods in industries utilize this method

Sequential Sampling

Ø Randomly select sample.

Ø Collect data at frequent intervals.

Ø Trend has to be studied.

Ø Examples: Sentinel surveillance data; Nutritional monitoring data; social changes.

Panel Sampling

c Sampling Error

c Prevalence of the condition

c Variability between sampling units (SD)

c Desired level of statistical significance (CI)

c Degree of difference/ Strength of Association to

be detected

- error and - error

Analytical Method: Pre-requisites

c Design of the study:

* estimating average or proportion

* Difference between two averages or proportions

Pre-requisites

Disparity between the true parameter and the sample statistic:

* Sampling error = 1/n n = sample size

* Larger the sample, lesser the sample error

Sampling Error

Sampling Error

Sampling Non-Sampling

Errors

CoverageType of controlsProcessing errorsObservational errors

If the prevalence of the condition is more; then sample size will be smaller:

Prevalence

Variability between sampling units (SD)

W Can be known by exploratory/ pilot study

eg. Weight gain in children after dietary supplementation

Less tolerable error = more the sample size:

Error

M Consult a statistician

M Refer to tables already availablea. For prevalence studiesb. For comparison groups

M Calculatea. Prevalence study( mean, proportions)

no = Z2 pq / e2

Z2 = abscissa of the normal curve that

cuts off an area at the tails

p = prevalence e = desired level

of precision

How to get a sample size ?

M In estimating Average or Proportion:

1. Parameter to be estimated

2. Degree of precision (tolerable Sampling error)

3. Desired confidence level

4. Estimated variability (SD)

M significance between proportions/ Means:

1. . Amount of difference of importance

2. Size of and error

3. Estimated variability (SD)

How to get a sample size ?

M Statistical Software.

How to get a sample size ?

Thank You