Conducting Research (2). Dr. Rasha Salama PhD. Community Medicine. Research . Research is the systematic collection, analysis and interpretation of data to answer a certain question or solve a problem It is crucial to follow cascading scientific steps when conducting one’s research.
Dr. Rasha Salama
PhD. Community Medicine
Selection of area
Selection of topic
Crude research question
Refined research question
Research hypothesis, goals and objectives
Population & sampling
Variables confounding bias
Collection of data
The process of sampling involves:
(exclusion criteria are not the opposite of inclusion criteria)
It is by far the most biases sampling procedure as it is not random (not everyone in the population has an equal chance of being selected to participate in the study).
“how many subjects should be studied?”
I. Effect size
II. Variability of the measurement
III. Level of significance
IV. Power of the study
“magnitude of the difference to be detected”
1. Avoid leading questions
2. Avoid questions that invite the social desirability bias
3. Avoid double-barreled questions
4. Avoid long questions
5. Avoid negations
6. Avoid irrelevant questions
7. Avoid poorly worded response options
8. Avoid big words
9. Avoid ambiguous words & phrases
“A false or mistaken result obtained in a study or an experiment” John last, 2001.
“ an error having a certain magnitude and direction repeated with every measurement”
“ error with no fixed pattern of magnitude or direction”
(intra and inter obs. Bias)
Study selection bias
Information bias is a distortion in the estimate of effect due to measurement error or misclassification of subjects according to one or more variables.
An error of categorization may occur if information on the exposure variable is unknown or inaccurate.
The recall by both cases and controls may differ in both amount and accuracy. Cases are more likely to recall exposures, especially if there has been recent media exposure on the potential causes of the disease.
Example: In questioning mothers whose recent pregnancies had ended in fetal death or malformation (cases), and a matched group of mothers whose pregnancies had ended normally (controls), it was found that 48% of the former, but only 20% of the latter reported exposure to drugs.
“State in specific steps what exactly
will be done”
Frequency distribution tables
Percentages and percentiles
Measures of central tendency
Measures of dispersion
The researcher uses principles of biostatistics to test his hypothesis. Detection of proper statistical test depends on: