the study of how to collect/organize/analyze/interpret numerical information from a data set
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individuals
people/object included in the study (2 types)
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variables
characteristics of the individuals to be measured or observed (2 types)
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population data (parameter)
the data from each individual in the population of interest
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sample data (statistic)
comes from some individuals in the population of interest
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nominal level
applies to data that consists of names/labels/categories, order doesn't matter
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ordinal level
applies to data that can be arranged in order, not numerical
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interval level
numerical measurements with no true zero or the ratio isn't meaningful
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true zero
if the measurement is converted into other units then the result would be zero
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ratio level
data with meaningful ratios, have a true zero
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simple random sampling
selected randomly with a number table or computer, each individual/sample of the population has equal chances of being selected
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stratified sampling
population divided into several groups and then a simple random sample is drawn from each group
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systematic sampling
elements of the population are arranged in order and then every kth element is selected with a random starting point
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cluster sampling
population are is divided into sections and then some sections are randomly selected with every individual of each section included in the sample
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convenience sampling
has a time/location limit and not every individual of the population has a chance of being selected
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multistage sampling
using a combination of sampling methods to create smaller groups at each stage (not convenience, last stage is cluster)
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class requirements
every data value must fall into one of the classes the classes must not overlap the classes must be of equal width there must be no gaps between classes
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relative frequency
class frequency/total number of data values
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relative frequency percentage
relative frequency * 100
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cumulative frequency
sum of the frequencies for that class and previous classes
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mount shaped symmetric
T shaped, mean/median/mode are equal
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skewed to the left
rises to the right, mean
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skewed to the right
rises to the right, mode
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unimodal
only has 1 peak/mode
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bimodal
has 2 peaks/modes
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population mean
u, sum of xi over N (N is the population size)
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sample mean
x_, sum of xi, over n (n is the sample size)
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deviation
xi-mean (u or x_), negative=value below average, positive=value above average
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coefficient of variation
(standard deviation/mean) * 100, small=most of the data is split around the mean, large=data values are split everywhere
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