Lecture 5 Flashcards
an element, feature, or factor that is liable to vary or change
factor
a quantity that during a calculation is assumed to vary or be capable of varying in value
mathematics variable
a data item that may take on more than one value during the runtime of a program
computing variable
4 scale of measurement data types
nominal, ordinal, continuous(interval and ratio)
a measurement scale based on the classification of an observation according to the group to which it belongs – a process of categorization
nominal
examples of nominal classification
gender, political party, martial status
a measurement scale based on the classification of an observation according to its relationship to other observations
ordinal
examples of ordinal classification
poor, fair, good rating scale
numbers can represent __ and __ scale values but just because numbers are used doesn’t mean that they represent “true numbers” that can be added and subtracted
nominal and ordinal
a measurement scale characterized by equal units of measurement, zero point is arbitrary, the distance between any two numbers is of known size
interval
examples of interval classification
fahrenheit and centigrade temp scales
a measurement scale characterized by equal units of measurement and a true zero point at its origin
ratio
examples of ratio classification
mass, time
populations use __ for constants, not variables
greek symbols
samples use __ for variables
roman characters
measures of location or central tendency
mode, median, mean
the value of the most frequent measurement, most useful with the nominal scale, but may be used with any scale, there could be more than one
mode
the value of the measurement that falls in the middle when the measurements are arranged in order of magnitude
median
the point at which or below which 50% of the measurements fall
median
probably most useful with the ordinal scale, but may be used with higher order scales
median
the arithmetical average, the sum of the measurements divided by the total number of measurements
mean
most useful with interval or ratio measurements scales
mean
range, interquartile range, variance, standard deviation, coefficient of variation, standard error of the mean
measures of variability or dispersion
the difference between the largest and smallest measurements
range
Xmax - Xmin
range
X25th percentile - X75th percentile
interquartile range
s^2, MS, mean square
variance
the average of the square of the deviations of the measurements about their mean
variance
__ is considered in terms of the distance of each measurement from the mean, generally associated with the term “degrees of freedom, df)
variance
variance is determined by
find mean, subtract this mean from each measurement and square the result to eliminate negative numbers
the sum of squared in the first two steps on determining the variance is called ___
sum of squares
dividing the sum of squares in variance by the number in the smaple inus one gives us the __, gives us an unbiased estimate of the population variance
sample variance
the positive square root of the variance
standard deviation
the standard deviation is calculated by taking the square root of the
square root of the variance
measures the percentage of spread, unitless, allows for caparisons
coefficient of variation
states that the sampling distribution of the mean of any independent, random variable will be normal or nearly normal, if the sample size is large enough
central limit theorem
if we took several samples from a population, calculated the mean of each sample, and then calculated the SD of these sample means, we would have
the standard error of the mean
can be calculated from a single sample by dividing the SD by the square root of N
standard error of the mean
an estimate of the variability of individual measurements within a sample, also is used to measure variability of individual subjects around a sample mean
standard deviation
an estimate of the variability of sample means about the population mean, also is used to assess how accurately a sample mean reflects a population mean
standard error of the mean
