Biostat Flashcards
Biostat
1.Best test to dermine incidence?
2.which is always longitudinal, prospective and analytic?
3.sample frame is must for which sample technique?
Biostat
1.Best test to dermine incidence?-Cohort
2.which is always longitudinal, prospective and analytic?-RCT
3.sample frame is must for which sample technique?simple random sampling
1.Gold standard for evaluating new information?
RCT
What is equivalant to median?
50th percentile
Mean of sqaure deviation of individual value from central value?
Variance
Best sampling for small and homogenous group?
Simple random sampling
Best random sampling for heterogeneous group?
Stratified Random sampling
Best non random sampling for heterogenous group?
Quota sampling
Types of research?
- Quantitative research
- Qualitative research
- Basic (pure) research
- Applied (practical) research
- Descriptive research
- Analytical (explanatory) research
Types of variable?
Based on characteristics: (Example)
A. Quantitative (numerical): Vary in amount
1. Continuous: In decimal e.g. height, weight
2. Discrete: In integer e.g. family member
B. Qualitative (categorical): Vary in category
1. Nominal: e.g. sex, religion
2. Ordinal: e.g. tumor grading
Types of variable based on relationship to each other?
★Independent(Exposure)variable: ex: Cause,exposure,input
যেমন smoking
★ Dependant variable: যেমন Lunng Ca.Depends on smoking.
★Confounding vaiable :Independant কে যে এম্পলিফাই করবে।কিন্তু নিজে করবেনা,সেটাই confounding..
★ Intervening variable:Idependant টা সরাসরি আউটকাম করবে না। কিন্তু অন্য মাধ্যমে করবে।এই অন্য মাধ্যমটাই হলো intervening.. যেমন Salt(independent) HTN(intervening) এর মাধ্যমে HF করে
What is study design?
Scientific and ethical method of search to collect valid and reliable data.
Types of study?
A. Observational study: (no intervention only observe)
★Descriptive study –
Case study
Surveillance
Census
Cross sectional study
★Analytical study:
Case control study
Cohort study (Strongest)
Cross sectional study
B. Experimental study (interventional, Do & Observe)
Clinical trial (study on human)
RCT (randomized controlled trial)
Non randomized controlled trial
Criteria of retrospective study?
★Moves from outcome to exposure
★Deals with pervious data
★ Backward looking study e.g. history of smoking in lung cancer
Criteria of prospective study?
★Moves from exposure to outcome ★Deals with future data
★Forward looking study e.g. clinical outcome of angioplasty in CAD.
Criteria of longitudinal study?
★Data collected at more than one point of time
★Follow up given on same study subjects
★Mostly prospective but may be retrospective
Criteria of cross sectional study?
Enrolment: a cross section of population (By neither exposure nor outcome)
★ Measures exposure & outcome simultaneously
★ No follow up; only finds what is happening right now
Criteria of Case control study?
By outcome; independent of exposure
Features:
★Observational
★retrospective
★analytical
(Polar থেলে p&L বাদ)
Criteria of cohort study?
Enrolment: by exposure; all outcome free
★Compare future outcome in two groups
★Features: observational, prospective/retrospective, longitudinal, analytical.(POLAR)
★★★Good for rare exposure.
★★★we can found incidence rate&relative risk
Biostat
Q. Negative predictive value affected by….. ?
Prevalence
Features of RCT
★Involve human volunteer
★ Interventional
★ Prospective
★longitudinal
★analytical
★Randomized (Essential feature)
Blinding (masking): Ignorance about the treatment status of participants..Types?
Single,double and triple
Types of Random sampling?
Random (probability or representative) sampling done by lottery or random process
★ Simple random sampling
★ Systematic random sampling
★ Stratified random sampling
★Cluster sampling
★Multi stage sampling (area sampling)
★ Multi phase sampling
Examples of Non random sampling?
Non random (non probability or non representative) sampling done without lottery / random process
★ Convenient (accidental) sampling
★ Purposive (judgment) sampling
★ Quota sampling
★Snowball sampling
Measures of Location?
➢ Measures of central tendency: Mean, median, mode.
➢ Percentiles
➢ Deciles
➢ Quartiles
Use of the measures of central tendency
➢ Quantitative data: Mean, median & mode
➢ Nominal data: Mode
➢ Ordinal data: Median & mode
Measures of Dispersion
Range
Mean deviation
Standard deviation
Variance
Inter quartile range
Inter decile range (IDR)
Coefficient of variation (CV
Features of Normal Distribution
★Bell shaped & bilaterally symmetrical ★Mean, median & mode coincide
★ About 50% values above & 50% values below the mean
★ Maximum values lie in the middle around the mean
Regarding SD
Mean ± 1SD covers 68% values
Mean ± 2SD covers 95% values
Mean ± 3SD covers 99% values
Right Skew Distribution (asymmetric)
Curve skewed to the right.
Higher frequency at lower values.
Lower frequency at higher values e.g. marks of hard examination.
Left Skew Distribution (asymmetric)
Curve skewed to the left
Higher frequency at higher values
Lower frequency at lower values
Graphs: for quantitative data
Histogram
Frequency polygon
Frequency curve
Line chart
Scattered diagram
Box-plot
Stem & leaf plot
Charts / diagram: for qualitative data
Simple bar diagram
Multiple bar diagram
Component bar diagram
Pie diagram
Pictogram
Map diagram
Categories of Test of Hypothesis.
Parametric test:
Parametric test: Quantitative data with normal distribution e.g.
t-test
Z-test
F-test (ANOVA)
Pearson’s correlation coefficient test
Categories of Test of Hypothesis.
Non parametric:
Non parametric test: Qualitative data Quantitative data with skewed distribution e.g.
Chi-square test
Proportion test
Spearman rank correlation test
Fisher exact test
Mann-Whitney U test
Students ‘t’ Test (unpaired) Preconditions:
Comparison between two means of two separate groups.
Quantitative data with normal distribution.
Unpaired design
Sample size less than 30
Students ‘t’ Test (Paired) Preconditions:
Comparison between two means of two dependent groups
Quantitative data with normal distribution
Paired design
Preconditions for ANOVA (F-test)
Comparison among the means of >2 groups.
Quantitative data.
