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AP Statistics Semester 1 Vocab

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Individuals
the objects, subjects or observations described by a data set, usually denoted by Xi
Quantitative Variable
a variable that takes on a numerical value for which it makes sense to do arithmetic operations like averaging
outlier
an individual observation that fall outside the overall pattern of any graph of data
Type 2 Error
An error made by failing to reject (accepting) the null hypothesis when in fact it is false
Law of large numbers
a property that states as the number of observations increases, the mean (statistic) of the observed values gets closer and closer to the true parameter
p-value
the probability of observing a value for a test statistic as extreme or more than the hypothesized given value
linear relationship
the relationship between two variables when the plotting of them in a scatterplot depicts a straight-line pattern
data analysis
the method of collecting, organizing, and then describing data using graphs, numerical summaries in order to make statistical inferences
placebo
a dummy treatment that has NO physical affect. Used in control gropus
Statistically significant
an observed effect too large to attribute plausibly to chance
extrapolation
the statistically unsound method of using a regression line to make predictions outside the range of values
categorical variable
a variable that belongs to one of many levels or groups. A proportion is formed by counting how many of the observations belong to the individual groups.
central limit theorem
as a randomly collected sample size gets large enough, the sampling distribution becomes more normal regardless of population distribution
standard deviation
a numerical value that measures the spread of a distribution by looking at how far the observations are from the mean
standard normal distribution
a bell shaped distribution with mean = 0 and standard deviation = 1
explanatory variable
a variable that is used as an attempt to explain the observed outcomes
correlation
a numerical value that measures the strength and direction of the linear relationship between two quantitative variables
lurking variable
a variable that has a significant effect on the response variable in the relationship between two variables in a study, but is not one of the two variables being studied
statistical inference
drawing conclusions about data after performing statistical procedures
Simpson's Paradox
this refers to a reversal of the direction of a comparison of an association when data from several groups are combined to form a single group
residual
the difference between an observed value and the predicted value (y-y(hat))
variable
any measurable characteristic of an individual (quantitative or categorical)
double blind experiment
an experiment in which neither the subjects nor the people conducting the experiment know which treatment a subject receives
power
the probability that a fixed level of significance will correctly reject a false null hypothesis
sample
the part of the population that we actually select and examine
undercoverage
this occurs when some groups in the population are left out of the process of choosing a sample
type 1 error
an error made by rejecting the null hypothesis when in fact it is true
Voluntary Response
a statistically unsound method of survey in which people choose themselves by responding to a general appeal
Matched Pairs Design
an experiment in which the subjects are matched in pairs and each treatment is given to one subject in each pair
Biased
a study that systematically favors certain outcomes
Distribution
the pattern of a data set. It tells us the range of the variable, the frequency of each value, the center, and the shape (normal or skewed) of the data.
Stratified Random Sample
a sample collected by dividing up the population into homogeneous groups and then using an SRS to sample from each group
Robust
a confidence interval or the outcome of a significance test that is unchanged when the assumptions are violated OR a resistant statistical procedure
Non-Response
this occurs when an individual chosen for a sample can't be contacted or refuses to cooperate
Standard Error
this is the estimated standard deviation computed from a sample of data
Unbiased Statistic
a numerical value that is estimated from a sample distribution that is equal to the true value of the population (statistic=parameter)
Random
a surveying or experimental phenomenon that occurs when the individual outcomes are uncertain
Null Hypothesis
the statistical hypothesis that states that there is no effect or no change in the claimed population parameter
Population
the entire group of individuals that we want information about
Parameter
a numerical value that describes the average of the population
Confidence Interval
an interval computed from sample data by a method that has a certain insurance of producing an interval containing the true population parameter
Probability
the proportion of times the outcome would occur in a very long series of repetitions
Critical Value (upper)
a numerical value, z or t that has probability = p, lying to the right of it under the standard normal curve
Statistic
a numerical value computed from a sample of data
Control Group
a group of individuals or experimental units that receive the placebo treatment
Treatment
a specific experimental condition applied to the units in order to change the environment to detect a significant effect
Experimental Units
the individuals on which the experiment is done on
Least Square Regression
the line that makes the sum of squares of the vertical distances of the data points from the lines as small as possible. Used for making predictions.
Square of the Correlation
r-squared, the fraction of variation in the values of y that is explained by the least-squares regression of y on x
Time Plot
a graph that depicts each observation against the time at which it is measured
Response Variable
a variable that measures an outcome of a study
Center, Spread, Shape
ways of describing the overall pattern of a distribution's histogram or timeplot