Transcript Materials & Method

Scientific Writing
MEST 201
Pr.Dr.Ramez Bedwani
Outcomes:
By the end of this lecture, the student will •
be able to Know definition, uses and types
of statistics.
Material And Methods
Patients And Methods
Material and Methods, Why?
Details that can help any researcher to
follow the same steps.
Assure generalizability.
Assure avoidance of different types of
bias.
Materials And Methods
Title page
Abstract
General Advice
Introduction
Materials &
Method
New methods are described in details. •
Results
Discussion
Summary
References
Tables
Figures
Legends to
Figures
Previously published methods: •
Common:Enumeration+ref.
-
Uncommon: Short summary + ref.
Which tense to use in the Methods
section
Use past tense throughout: •
“We recruited 143 patients with moderate –
persistent asthma ….”
Material and Methods, What?
1. Research Design.
2. Setting.
3. Selection of Study Population.
4. Sample size calculation.
5. Data collection and Operational definition of variables.
6. Procedures.
7. Materials.
8. Statistical methods.
9. Ethics.
Material and Methods, What?
1-Research Design
Research Design:
plan chosen to answer the research Q.
Research Objective VS Research Design
Estimation ------ Cross Sectional Study
Association ---- Case Control Study
Cause Effect Relation -- Cohort Study
Evaluation of Intervention- Clinical Trial
Research Design Statement
Example
Research Design :
Cross sectional study
Case Control Study
Cohort Study
Double Blind Randomized Clinical
Trial
Material and Methods, What?
2- Setting
Setting
e.g.
Out patient, Hospitalized patients, Cases in ICU
Health units in rural areas, ……..
Setting Statement
Example
Study Setting:
The study was conducted in a semi rural area located
about 25 miles from the city Karachi, Pakistan”
“ Maternal Charctersitics in relation to income in ………..”
Eastern Mediterranean Health Journal, 13, 6, 2007
Material and Methods, What?
3-Study population



Sampling method
Inclusion and exclusion criteria
Method of allocation of groups
Population and Sampling
Population: what was the source of the •
population studied?
Dates of Data Collection: give the period •
over which data were collected.
Population and Sampling
Selection: How were individuals selected •
into the study?
Inclusion criteria
Exclusion criteria
Clinical and pharmacological variables as a risk factor
for
nifedipine-induced gingival overgrowth
Eighteen patients taking nifedipine in regular
doses for at least six months ( EXPOURE)
participated in the study between 2003–2005.
Prior approval was received from the Ethics
Committee. Patients enrolled in this study were
obtained from outpatients attending the
Cardiology Department at the Faculty of
Medicine,Hacettepe University ( SETTING).
Australian Dental Journal 2007;52:(4):295-299
Clinical and pharmacological variables as a risk factor
for
nifedipine-induced gingival overgrowth
Only patients who possessed at least 12 anterior teeth in
both upper and lower arches participated in the study.
Mean daily nifedipine dose was 30 mg in all patients.
Exclusion criteria were:
smoking, periodontal treatment undertaken less than
six months prior to the baseline visit, concomitant
systemic disorders known to affect the periodontal
tissues, and use of phenytoin and cyclosporine. Patients
with periodontitis (both treated and untreated) were
also excluded from the study
Australian Dental Journal 2007;52:(4):295-299
Material and Methods, What?
4.Sample size calculation.
Sample Size is critical to precision of the estimate
and power of the study.
Factors Affection Sample Size
Calculation
Confidence level (1- )
Power (1- )
SD
Sample Accuracy
Sample Size Statement
Example
Sample size required is 30 to achieve 80% •
power at 5% level of significance, provided
that prevalence of the outcome is …% and
maximum error in estimate equal to … %.
Reference: •
The sample size was calculated using NCSS 2004 and
PASS 2000 Program.
•
Sample Size Statement
Example
….. to detect a mean difference of at least 10 mm
Hg The minimum sample size required in each
group is 52 to achieve a study power of 80%
and level of confidence 95%.
References: •
The sample size was calculated using Medcalc Program version
8.1NCSS 2004 and PASS 2000 Program.
5. Data collection and Operational definition
of variables
Operational definition of outcome variables
and independent variables.
Main variables
Outcome variables: •
Dependent variables –
In observational studies: what you are trying –
to predict
In Clinical trials: endpoints: –
Primary
Secondary
Main variables
Exposure Variables
Main exposures of interest
Confounders/Effect modifiers
Main Variables
Operational definition of variables
Transformation of variables
Creation of categorical variables
Why?
Number of levels?
Predefined levels or quantiles?
Measurements
Who made the measurements?
What qualification did they have for the
job?
What training was undertaken?
Were they and/or the patients masked
(blinded)?
Measurements
Conditions of measurement •
Sitting, standing,… after 10 minutes rest, … –
Instrumentation •
Including model, source and supplier of –
instruments
Precision of measurements •
Source of consumables •
Data Collection and definition of Variables
e.g. BMJ. 2006 March 4; 332(7540): 521–525.
Chronic stress at work and the metabolic syndrome: prospective study
•
Data on the components of the metabolic
syndrome were collected during the clinical
examination, using the definition of the National
Cholesterol Education Program by the presence
of three or more risk factors( Ref).
We used obesity (defined as body mass index >
.30) as an indicator of risk for the syndrome
Data Collection and definition of
Variables
e.g. BMJ. 2006 March 4; 332(7540): 521–525.
Chronic stress at work and the metabolic syndrome: prospective study
Data collection and definition of Variables :
Data on the components of the metabolic syndrome were
collected during the clinical examination, using the
definition of the National Cholesterol Education Program
by the presence of three or more risk factors( Ref).
We used obesity (defined as body mass index > 30) as an
.indicator of risk for the syndrome
Clinical and pharmacological variables as a risk factor
for
nifedipine-induced gingival overgrowth
definition of Variables
Gingival overgrowth was assessed in both vertical
and horizontal dimensions at each papilla on the buccal
and lingual aspects. A total of 20 dental papilla
(10 maxillary papilla and 10 mandibular papilla) were
evaluated in each patient in the anterior region. The
height of the gingival tissue was measured from the
cemento-enamel junction (CEJ) to the free gingival
margin according to Miller and Damm’s index (0, 1, 2,
3 scores).16
Australian Dental Journal 2007;52:(4):295-299
5. Data collection and Operational definition
of variables: Measurement
. Measurement
(validity, reliability, precision)
5. Data collection and Operational definition
of variables
• 8. Material
e.g. Identify precisely all drugs and
chemicals used including: generic names,
doses and routes of administration.
6. Procedures
Describe: •
Surgical technique. •
- Radiological technique.
•
•
Material
If drug (preparation, dose, •
timing…etc).
8- Statistical methods.
– Describe in details
Assumptions for Statistical Analyses
Independence, normal distribution, multiple
measurements, …….
Statistical analysis
Mann Whitney U-test test was used to compare data in
responders and non-responders. For correlations
between GCF–plasma drug concentrations, clinical
parameters and demographic parameters, Spearman’s
correlation rank was used. Fischer’s exact test was also
used to determine the difference between males and
females.
Statistical methods Statement
Example
Statistical Analysis
We used logistic regression analysis to
assess the odds ratios of the metabolic
syndrome for the different explanatory
variables
BMJ. 2006 March 4; 332(7540): 521–525. •
Chronic stress at work and the metabolic syndrome: prospective
study
•
A few words about math…
Equations are often necessary to describe in •
the methods
Peripheral equations should be avoided or •
moved to an Appendix –
Define all terms in your equations. •
Statistical Analysis
What comparisons were made? •
In trials was the comparison by “intention to –
treat” or “per protocol”?
Using what technique? •
What software was used and (where •
relevant) which programs?
(What p-values were taken to be •
significant)
Statistical Analysis
Justify any sub-group analyses: •
Were they in the original protocol? –
Why were they done? –
Were they post-hoc, because you didn’t find –
what you originally expected?
Title page
Abstract
9- Ethics
Introduction
Materials &
Method
Results
Discussion
Ethical permission must be
Summary
References
Tables
acknowledged in the methods
Figures
Legends to
Figures
section.
Title page
Abstract
Evaluation of the
Materials and Methods
Introduction
Materials &
Method
Results
Discussion
Summary
References
Tables
Figures
Legends to
Figures
The reviewer asks the following questions :
1- Is the study population detailed
adequately ?
2- Are the methods described well enough to
reproduce the experiment ?
3- Is the study design clear ?
4- Are statistical methods included ?
Assignment
Topic
Student Names
Types Statistical
Analysis
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