variables Flashcards
briefly explain the 2 groups of statistical data
constant: remains the same from time to time/ place to place
- fixed value
- value of pi
- pull of gravity
- speed of light
variable:
information on any characteristics that can be varied
it changes over time (example: smoking habits, weight, educational attainment)
2 kinds are…
- qualitative
- quantitative
briefly explain qualitative variables and quantitative variables
qualitative:
described by features, generally by words
used as labels to distinguish one gro from another (ex: skin color, religion, gender)
cannot be used as a basis to say that one grp is greater or lesser or higher or lower or better or worse than other grp
quantitative:
values expressed numerically
can be measures and ordered according to quantity or amount - rank lowest to highest (blood pressure, birthweight, height and weight)
what are the diff levels of measurement
nominal
dichotomous
ordinal
interval
ratio
variables that have no measurement scales and no rank order
nominal
nominal (example)
under qualitative
numeric variables may be assigned to these categories as labels but will not affect the statistical analysis - to shorten encoding
(No. 1 = normal skin color,
no. 2 = tan, no. 3 = dark,
no. 4 = very dark
○ Different blood groups
○ Vegetable and fruit color)
variables that only have two labels
dichotomous
dichotomous in greek (examples)
dicho -into
temnein - to cut
(○ Normal and abnormal skin
color
○ Biological gender
■ Male
■ Female
○ Health status
■ Well
■ Sick)
variables that can be ranked or ordered
ordinal
ordinal (examples)
can either be qualititative or quantitative depening on the objective of the data collection
arranged from the highest to lowest
(○ Severity of diseases
○ Physical activity level)
there are equal intervals between values and have a true zero point
ratio
values are separated by equally spaced intervals and have no true zero point
interval
interval (examples)
No true zero: There’s no absolute zero point. The zero is just a placeholder and doesn’t mean “none” or “absence” of the thing being measured.
Limited math: You can add and subtract these values, but multiplying or dividing them doesn’t make sense.
(Temperature (in Celsius or Fahrenheit), IQ scores, and calendar dates)
The difference between 10°C and 20°C is the same as the difference between 20°C and 30°C (equal intervals).
0°C doesn’t mean “no temperature” - it’s just the freezing point of water (arbitrary zero).
We can say it’s 10 degrees warmer today than yesterday (meaningful difference).
But we can’t say 80°C is twice as hot as 40°C (multiplication doesn’t work).
ratio (examples)
(○ Height and weight - someone cannot be negative or 0 kg and m.
○ Distances
○ Temperature in Kelvin)
data can be added, subtracted, multiplied or divided
someone who is 100kg is twice as heavy as someone who is 50kg
rank the levels of measurement from the most info to the least info
ratio
interval
ordinal
dichotomous
nominal
differentiate discrete data and continuous data
discrete data:
integers (whole no.)
no decimal point for fraction
continuous point:
have fractional data (ex: 3..5 or 1/2)
the difference between 2 numbers are infinite - means that number between 3 and 4 is never ending
