Chapter 1 - Descriptive Stats Flashcards
A ________ variable can be described by a number for which arithmetic
operations such as averaging make sense.
Quantitative Variable
A ________
variable simply records a quality. If a number is used for distinguishing
members of different categories of a qualitative variable, the number
assignment is arbitrary.
Qualitative Variable
Numbers are used simply as labels for groups or classes. If our data is green, blue, etc we can assign labels 1=blue and green=2
Nominal scale
Data elements may be ordered according to relative size or quality in this scale. 1, 2, 3 ,4 where 4 is the worst.
Ordinal Scale
Zero is assigned arbitrarily in this scale. 10am is not twice as long as 5 am, but the interval between 0-5 and 0-10 am is twice as large.
Interval scale
Zero in this scale is absolute 0. 50$ is half as much as 100$
Ratio scale
Population/universe or sample?
______consists of the set of all measurements in which the investigator is interested.
Pupulation/universe
Population/universe or sample?
Subset of measurements within the universe.
Sample
A set of measurements obtained on some variable is called a ____ ____. For example,
heart rate measurements for 10 patients may constitute a ____ ____
data set x2
This is the biasing of the results that occurs when we disregard
the fact that some people will simply not respond to the survey. The bias distorts the
findings, because the people who do not respond may belong more to one segment
of the population than to another.
Non response bias
In experiments, as in surveys, it is important to _______ if inferences are
indeed to be drawn.
randomize
Percentile formula
(n +1)P/100, where n is the number of data points and P is the percentile we are looking for.
The median is what quartile?
The 2nd quartile or 50%.
Interquartile is the range between the _ and _ quartiles
1st and 3rd (25%-75%)
Interquartile range formula
3rd-1st quartile points= x
The measures of central tendency include
Mean, Median, and Mode.
The mode is
The data set value that occurs most frequently
The mean is the
equal to the sum of all observations divided by the number of observations in the set.
What type of measure is the interquartile range?
Measure of variability
The range is a measure of ___
variability
The range is equal to
The largest number minus the smallest number
Variance is equal to
the average squared deviation of
the data points from their mean.
The square root of the variance
is the the standard deviation
