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Presented at CRC course held at King Fahad Medical City, Riyadh on 26 January 2020. 11:00 am - 12:00 pm by Professor Omar Hasan Kasule Sr. MB ChB (MUK). MPH (Harvard), DrPH (Harvard) Chairman of the Institutional Review Board, King Fahad Medical City
INTRODUCTION:
} For a critical reading of scientific literature, the reader must be equipped with
tools to analyze their methodology and data analysis critically
before accepting their conclusions.
} Common
problems in published studies are incomplete documentation, design
deficiencies, improper significance testing and interpretation.
ISSUES IN THE TITLE:
} The main
problem of the title is irrelevance to the body of the article.
} Too long
and too short.
} Title
lacking key words of the research.
PROBLEMS OF THE ABSTRACT:
} Failure to
show the focus of the study.
} Failure to
provide sufficient information to assess the study (design, analysis, and
conclusions).
} Focusing on
only one part of the study.
} Including
literature review and taking much space.
PROBLEMS OF THE INTRODUCTION:
} Failure to state the reason for the study.
} Failure to
review previous studies, succinct and relevant.
} The laundry
list of previous studies.
} Failure to
point out the gap in knowledge and the contribution of the present study.
} Failure to
provide the background and historical perspective.
} Failure to
state the study population.
} Failure to
state the study hypothesis.
PROBLEMS OF
STUDY DESIGN:
} Going on a
fishing expedition without a prior hypothesis.
} Study
design not appropriate for the hypothesis tested.
} Lack of a
comparison group.
} Use of an
inappropriate comparison group.
} The
Berkson's fallacy.
} Selection
of cases and controls from different populations.
} Sample size
not big enough to answer the research questions.
PROBLEMS OF CONFUSED TERMINOLOGY:
} ‘Measurement’
uses instruments. ‘Calculation’ deals with numbers and formulas.
} ‘Estimation’
is used in two senses as an approximation in measurements or as computation of
statistical parameters.
} ‘Determination’
is a general term for getting to a conclusion by use of the 4 methods above.
} The term
‘study’ is generic and can be confused with experiment that refers to only some
types of studies.
PROBLEMS IN DATA COLLECTION:
} Missing
data due to incomplete coverage,
} Loss of
information due to censoring and loss to follow-up,
} Poor
documentation of data collection,
} Methods of
data collection inappropriate to the study design.
PROBLEMS OF DATA ANALYSIS:
} Failures to
state the type of hypothesis testing (p value or confidence interval).
} Use of the
wrong statistical tests mostly because of confusing discrete and continuous
data.
} Drawing
inappropriate conclusions.
} Use of
parametric tests for non-normal data.
} Multiple
comparisons or multiple significance testing.
} Failure to
assess errors.
} Failure to
assess normality of data.
} Failure to
use the appropriate data scale: qualitative/quantitative/discrete/continuous.
} Using the
wrong statistical formula.
PROBLEMS IN REPORTING RESULTS:
} Selective
reporting of favorable results,
} Numerators
without denominator,
} Inappropriate
denominators,
} Numbers
that do not add up,
} Tables not
labeled properly or completely,
} Numerical
inconsistency (rounding, decimals, and units),
} Stating
results as mean +/- 2sd for non-normal data,
} Stating p
values as inequalities instead of the exact values,
} Missing
degrees of freedom and confidence limits.
PROBLEMS OF THE CONCLUSION - 1:
} Repeating
the results section,
} Failure to
discuss the consistency of conclusions with the data and the hypothesis,
} Extrapolations
beyond the data,
} Failure to
discuss short-comings and limitations of the study,
} Failure to
evaluate statistical conclusions in view of testing errors,
} Failure to
assess bias (misclassification, selection, and confounding).
PROBLEMS OF THE CONCLUSION - 2:
} Failure to
assess precision (lack of random error), and assessment of validity (lack of
systematic error).
} Failure to
appreciate the difference between internal and external validity: Internal
validity is achieved when the study is internally consistent and the results
and conclusions reflect the data. External validity is generalizability (i.e.
how far can the findings of the present study be applicable to other
situations) and is achieved by several independent studies showing the same
result.
} Inability
to detect the outcome of interest due to insufficient period of follow-up,
inadequate sample size, and inadequate power.
ABUSE OR MISUSE OF STATISTICS:
} Incomplete
and inaccurate documentation of results.
} Selection
of a favorable rate and ignoring unfavorable ones. This is done by 'playing'
either with the numerator or the denominator.
} The scales
of numerators and denominators can be made artificially wider or narrower
giving false and misleading impressions.
MISLEADING STATISTICS:
} Violating
the principle of parsimony.
} Study
objective unclear and not reflected in the study hypothesis.
} Fuzzy,
inconsistently, and subjective definitions (of cases, non-cases, the exposed,
the non-exposed, comparison groups, exposure, method of measurement).
} Incomplete
information on response rates and missing data.