Stats Vocab
placebo
a dummy treatment with no active ingredients
table of random digits
a long string of digits ranging from 0 to 9 and are independent of each other
predictive validity
a measurement that can be used to predict success on tasks that are related to the property measured
parameter
a number that describes the population, a fixed number but we don't know the actual value
seasonal variation
a pattern that repeats itself at regular known intervals
measure
a property of a person or thing when we assign a number to represent the property
lurking variable
a variable that has an important effect on the relationship among the variables in a study but is not one of the explanatory variables studied
completely randomized
all the experimental subjects are allocated at random among all the treatments
double blind
an experiment in which neither subjects nor physicians recording the symptoms know which treatment was received
randomized comparative experiment
an experiment that compares just two treatments
outlier
an individual observation that falls outside the overall pattern of the graph
statistically significant
an observed effect of size that would rarely occur by chance
nonsampling error
are errors not related to the act of selecting a sample from the population, can be present in the census
variance
average squared distance
midpoint
center of distribution
voluntary response sample
chooses itself by responding to a general appeal
average
combining multiple measurements to get a more reliable result
matched pairs design
compares just two treatments
simple random sample
consists of individuals from the population chosen in such a way that every set of individuals has an equal chance to be the sample actually selected
five-number summary
consists of the smallest observation, the first quartile, the median, the third quartile, and the largest observation
experiment
deliberately imposes some treatment on individuals in order to observe their responses
variability
describes how spread out the values of the sample statistics are when we take many samples
quartiles
divide the information into quarters
sampling errors
errors caused by the act of taking a sample, cause sample results to be different from the results of a census
exhaustive
every individual appears in some class
seasonally adjusted
expected seasonal variation is removed before the data are published
clinical trails
experiments that study the effectiveness of medical treatments on actual patients
qualitative data
expressed in qualities
quantitative data
expressed with numbers
rate
fraction, proportion, percentage
histogram
graph of the distribution of a quantitative variable
block
group of experimental subjects that are known before the experiment to be similar in some way that is expected to affect the response to the treatment
subjects
individuals studied in an experiment
boxplot
is a graph of the five-number summary
probability sample
is a sample chosen by chance
census
is a sample survey that attempts to include the entire population in the sample
mean x
is a set of observations is their average
response
is a variable that measures an outcome or results of a study.
explanatory variable
is a variable that we think explains or causes changes in the response variable
variable
is any characteristic of an individual
treatment
is any specific experimental condition in applied to the subjects
bias
is consistent repeated deviation of the sample statistic from the population parameter in the same direction when we take many samples
random sampling error
is the deviation between the sample statistic and the population parameter caused by chance in selecting a random sample
population
is the entire group of individuals about which we want information
nonresponse
is the failure to obtain data from an individual selected for a sample
median
is the midpoint of a distribution, the number such that half the observations are smaller and the other larger
sample
is the part of the population from which we actually collect information and is used to draw conclusions about the whole
sampling frame
list of individuals from which we will draw our samples
trend
long term upward or downward movement
confidence statement
margin of error and level of confidence
valid
measure of a property if it is relevant or appropriate as a representation of that property
standard deviation s
measures the average distance of the observations from their mean
processing errors
mistakes in mechanical tasks such as doing arithmetic or entering responses into a computer
exclusive
no individual is in more than one class
statistic
number that describes a sample, value is known but can change from sample to sample
data
numbers with a context
observational study
observes individuals and measures variables of interest but does not attempt to influence the responses
response error
occurs when a subject gives an incorrect response
undercoverage
occurs when some groups in the population are left out of the process of choosing the sample
skewed
one side extends much farther than the others
categorical variable
places an individual into one of several groups or categories
line graph
plots observations against time at which it was measured
random error
repeated measurements on the same individual give different results
level of confidence
says what percentage of all possible samples satisfy the margin of error
convenience sampling
selection of whichever individuals are easiest to reach
pie charts
show the whole divided into parts
bias
statistical study systematically favors certain outcomes
dropouts
subjects who begin the experiment but do not complete it
nonadherers
subjects who participate but don't follow the experimental treatment
sample survey
survey some group of individuals by studying only some of its members
quantitative variable
takes numerical values for which arithmetic operations such as adding and averaging make sense
confounded
the effects on a response variable cannot be distinguished from each other
individuals
the objects described by a set of data. may be people, animals, or things
margin of error
the percentage that tells us how close our estimate comes to the truth 1/square root (n)
block design
the random assignment of subjects to treatments is carried out separately within each block
symmetric
the right and the left sides of the histogram are approximately mirror images
statistics
the science and art of data
stemplot
used for small data sets and is quicker and presents more detailed information
response variable
variable that measures an outcome or result of a study
distribution
what values a variable takes and how often it takes these values
unit
what we measure in and record the measurements
instrument
what we use to make a measurement