Variations in Biostat Flashcards
The tendency of a measurable characteristic to change
o From one individual or setting to another
o Within the same individual or setting at different periods of time
Statistics is necessary to analyze variability
Phenomenon of Variation
Non-changing: usually applicable to the physical sciences
Examples: speed of light, π, minutes in an hour
Constants
Measurement or a characteristic
Values that change within a category
Values vary from one individual to another or within the same individual at different periods of time
Examples: Age, gender, height, weight
Variables
____________ – the variable under investigation which is hypothesized to have an effect on the outcome ***independent variable – controlled
Independent variable
_______________ – the outcome of interest in the study ***it changes depending on something influences it
Dependent variable
________________– confounders. Other factors related to both dependent and independent variables ***it is “confounding variable”
Extraneous variables
Example
1: Internet
Educational networking
Compliance to Clinical Practice Guidelines
***Answer: independent variable – educational networking Dependent variable –compliance to clinical practice guidelines Extraneous variable – internet
Example
2: Menstrual cycle
Feminine wash
Vaginal pH
***Answer: independent variable –feminine wash Dependent variable – vaginal pH Extraneous variable – menstrual cycle
Example 3
: Feminine wash
Bacterial vaginosis
Fluconazole
***Answer: independent variable -fluconazole Dependent variable –bacterial vaginosis Extraneous variable – feminine wash OR independent variable –fluconazole + feminine wash Dependent variable – bacterial vaginosis Extraneous variable - none
Example
4:
Stone surgery
Sambong leaf
Kidney stones
***Answer: independent variable – stone surgery Dependent variable – kidney stones Extraneous variable – Sambong leaf OR independent variable –stone surgery + Sambong leaf Dependent variable –kidney stones Extraneous variable - none
Example 5:
Biopsy
Breast CA
Chemotherapy
***Answer: independent variable -chemotherapy Dependent variable –breast CA Extraneous variable - biopsy
Types of Variables
Qualitative vs. Quantitative Variables
o Sex, Educational Level, Occupation, Religion, Residence, Disease Status
o Merely labels to distinguish one group from another
o Numerical representation only for coding / labeling and not for comparison
Qualitative
____________
o Values indicate a quantity or amount and can be expressed numerically
o Values can be arranged according to magnitude
o Examples: Age, Height, Weight, BP, WBC Count, Hemoglobin level Levels of Measurement
Quantitative
Levels of Measurement
- nominal scale
- ordinal scale
- Interval scale
- ratio scale
______________
o Categories used as labels only
o Numbers / Names represent a set of mutually exclusive and exhaustive classes to which individuals or objects may be assigned
o Ex: Sex (M, F) Blood Type (A, B, AB, O) Patient ID, Disease Type ***mutually exclusive, ‘di pwedeng magbago, ikaw lang ang pwedeng magkaroon at ‘di pwedeng magamit ng iba
Nominal Scale
____________
o Categories used as labels (like nominal)
o Can be ordered or ranked
o However, the distance between two categories cannot be clearly quantified
o Ex: Psychosocial scales (Strongly agree, agree, disagree, strongly disagree)
o Age Groups (Infant, child, teenager, adult)
Ordinal Scale
____________
o Same characteristics as ordinal scales
o Distances between all adjacent classes are equal
o Scales are infinite.
Zero point is arbitrary and does not mean the absence of the characteristic
o Ex: Calendar Time, Temperature, IQ ***zero is arbitrary – merong meaning ang zero -example: Temp- 0 °C (freezing point)
Interval Scale
o Same as for ordinal scales with the additional feature that a meaningful zero point exists
o Ex: Weight, Blood Pressure, Height, Number of Teeth ***walang meaning ang zero Ex. # of teeth- 0
Ratio Scale
Variable :Age
Measurement Scale:Measured in years
Ratio
Variable :Blood Type
Measurement Scale:A, B, AB, or O
Nominal
Variable :Asthma severity
Measurement Scale:Mild, Mod, Severity
Ordinal
Variable: Diastolic BP
Measurement: Mm Hg by sphygmo
Ratio
variable:Weight
Measurekent: Kg using weighing scale
Ratio
Variable: Cigarette smoking
Measurement: Cigarette count
Ratio
Variable:Live Births
Measurement :Birth rate
Ratio
variable: Level of difficulty of a subject
Measurement: Easy, difficult, very difficult
Ordinal
Variable: Global efficacy of a treatment
Measurement: Great improvement, moderate improvement, no change, worse
Ordinal
variable:Religion
Measurement: Cath, Prot, Muslim, etc.
Nominal
Variable: Body Temp Temp in C°
Measurement :by thermometer
Interval
Variable: Level of awareness of a WHO guideline
Measurement :Aware, heard about it, not aware
Ordinal
