sample
selects a subset of a population
population
measures every individual
random
method where each individual has equal probability of being selected
stratified
sample that is proportional to the size of a demographic in a population
voluntary
sample that contains only those individuals that choose to participate
cluster
method that selects small groups selected randomly by geography or association
convenience
sample includes those that are easiest to collect data from
systematic
methods that uses a rule or pattern to select an individual
destructive
method that destroys the individual in order to collect the data
bias
systematic error in an experiment that over or under measures
validity
experimental results are reproducible by others
reliable
conclusions made from the data make credible predictions
primary
source of data collected or recorded first hand
secondary
source of data collected and interpreted by someone else
categorical
data collected by a description rather than measured
continuous
variable of measured data (uncountable outcomes)
discrete
variable that contains data from a countable set of outcomes
histogram
graphical depiction of continuous one variable data
bar graph
graphical depiction of discrete data
normal
data where measures of central tendency are equal or sufficiently close
skew
the mean is pulled away from the other central measures
outlier
an anomalous datum that is separated from or doesn't match the pattern in the rest of the data set
mean
average of a data set
median
middle value of a sorted data set or the 50th percentile
mode
most frequent value of a data set
range
the minimum value subtracted from the maximum value
variance
average area of squares defined by each piece of data to the mean of the data set
standard deviation
square root of the variance
inter-quartile range
the first quartile subtracted from the third quartile
quartiles
divides the data set into four equally sized subgroups
box and whisker
graphical depiction of quartiles with the median
bimodal
has two modes outside of the mean and median
accuracy
how close the data is to the correct value
precision
how close the data points are in relation to each other
inferential
statistics that extrapolate to the entire population
descriptive
statistics used to describe a data set
quantitative
numerical measures of discrete or continuous variables
qualitative
anecdotal observations or categorical data
variable
an attribute that measured or counted
coefficient of determination
r^2 value that measures how much the change in the dependent variable can be explained by the change in the independent variable
linear regression
an algorithm to find the equation of line of fit for a set of data
correlation coefficient
the PPMC for a data set that indicates the strength and direction of the linear relationship between -1 and 1
PPMC
Pearson Product Moment of Correlation also known as the correlation coefficient or r-value
cause and effect
a relationship in which change in the independent variable causes change the dependent variable
influential point
an extreme data point that affects the slope of the line of best fit and increases the coefficient of determination
percentile
breaks a data set into 100 equal parts and is used to rank data
weighted mean
an average calculation where each piece of data has a component factor used to amplify or diminish it
index
an actual, relative, or subjective value that is tracked over time
real value
used to compare the value of investments after inflation has been discounted
sample bias
occurs when the participant group does not reflect the population that is being studied or a sample is too small
non-response bias
occurs when subgroups are under-represented because of low participation rates
measurement bias
occurs when the device used for the experiment is not calibrated accurately
response bias
occurs when participates purposely provide false or misleading answers
reverse cause and effect
when the independent and dependent variables are reversed
presumed relationship
when the dependent variable is assumed to be related to the independent variable
accidental relationship
when the independent variable is not related to the dependent variable
common cause
when the change in independent and dependent variable are caused by an outside factor