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Statistics
stats 221 exam 2
49
Mathematics
Undergraduate 2
03/13/2008

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Term
alternative hypothesis
Definition
The hypothesis that the researcher usually wants to prove or verify. Value is either <, >, or =
Term
association
Definition
values of one variable tend to occur with certain values of another variable; detected with the conditional distributions differ from the marginal distributions and from each other
Term
bias
Definition
a condition where the mean of the statistic values differs from the parameter that the statistic estimates
Term
bivariate data
Definition
data collected on two variables for each individual in a study
Term
C
Definition
the symbol for level of confidence (this isn't alpha - alpha is level of significance)
Term
Central Limit Theorum
Definition
the sampling distribution of xbar is approximately normal whenever the sample is large and random
Term
conditional distribution
Definition
the distribution of the values in a single row or a single column of a two-way table
Term
conditions for the sampling dist. of x bar to be approximately normal
Definition
sample size is large and sample is random (CLT application)
Term
conditions required for the sampling dist. of x bar to be normal
Definition
original pop. is normal and sample is random
Term
confidence interval
Definition
a list of reasonable values (with an associated level of confidence) for the parameter based on a value of a statistic
Term
control chart
Definition
a statistical tool for monitoring the input or output of a process
Term
control limits
Definition
mu - 3 times sigma over the square root of n and mu + 3 times sigma over the square root of n. Used to detect out-of-control signals in a control chart
Term
correlation coefficient
Definition
r - a measure of the strength of the linear relationship between two quantitative variables.
Term
decreased
Definition
when sample size is increased the width of the confidence interval is __________
Term
disjoint events
Definition
events that cannot occur at the same time (simultaneously)
Term
distribution of a variable
Definition
a list of the possible values of a variable together with the frequency of each value. (Note: probabilities can be given instead of frequencies.)
Term
event
Definition
a single outcome or a compbination of outcomes from a random phenomenon
Term
extrapolation
Definition
predicting a value for a value that is beyond what is in the data. This is bad because the prediction could be way off so it shouldn't be done at all
Term
garbage
Definition
results from statistical analyses performed on non-random samples
Term
increased
Definition
when the level of confidence is increased the width of the confidence interval is ________.
Term
inference
Definition
using results from a sample statistic value to draw conclusions about the population parameters. (Using what we learn about the sample to give us information about the target population)
Term
influential observation
Definition
an observation that substantially alters the values of slope and y-intercept in the regression equation when it is included in the computations (an outlier)
Term
law of large numbers
Definition
the fact that the average (x bar) of observed values in a sample will get closer and closer to mu as the sample size increases
Term
laws of probability
Definition
the basis for hypothesis testing and confidence interval estimation
Term
least squares
Definition
a method for finding the equation of a line that minimizes the sum of squared residuals (the line that has the smallest sum of squared residuals)
Term
least squares regression line
Definition
the line with the smallest sum of squared residuals
Term
level of confidence
Definition
the percentage of the time that the confidence interval procedure will produce confidence intervals that contain the parameter being estimated; don't ever use probability in a sentence about this if there is already data collected and an interval computed.
Term
marginal distribution
Definition
the distribution of values in the margins - the "total" row or the "total" column of a two- way table.
Term
margin of error
Definition
the maximum amount that a statistic value will differ from the parameter value for the middle (1-C) x 100% (this means level of confidence) of the distribution of all possible statistics.
Term
mean of the sampling distribution of x bar
Definition
the mean of all the sample means from all possible samples of size n from a population: equals mu
Term
mu
Definition
the mean of the population
Term
no association
Definition
a condition where values of one variable occur independent of values of another variable; detected when the conditionals of a two-way table equal the marginal distribution (and each other)
Term
null hypothesis
Definition
the hypothesis that the researcher assumes to be true until sample results indicate otherwise; the hypothesis of no difference or no change; hypothesis researcher usually wants to disprove
Term
observed effect
Definition
the difference between the observed statistic and the claimed parameter value
Term
one-sided or one-tailed
Definition
< or > in the Ha hypothesis
Term
out-of-control process
Definition
one sample mean outside three standard deviations of x bar or nine sample means in a row above or below the line
Term
outlier
Definition
an observation that falls outside the the overall pattern of the data set
Term
p-value
Definition
the probability of getting a test statistic as extreme or more extreme than the value observed assuming Ho is true
Term
parameter
Definition
a characteristic of a population that is usually unknown; this could be mean, median, proportion, standard deviation, computed on all the data from a population; a parameter does not have variability
Term
parameter symbols
Definition
mu, sigma and p (proportion of a population)
Term
positive association
Definition
high values of one variable tend to association with high values of another variable
Term
probabilitiy of an outcome
Definition
a measure of the proportion of times an outcome occurs in a very long series of repetitions that gives us an indication of the likelihood of the outcome.
Term
process
Definition
sequence of operations used in production, manufacturing, etc.
Term
process in statistical control
Definition
a process whose inputs and outputs exhibit natural variation when observed over time
Term
quality control chart
Definition
a chart plotting the means x bar of regular samples of size n against time; this chart is used to assess whether the process is in control
Term
quantitative bivariate
Definition
the type of data required for regression analysis
Term
r2
Definition
the percentage of total variation in Y that is explained by X
Term
r
Definition
correlation coefficient
Term
random
Definition
a phenomenon that describes the uncertainty of individual outcomes but gives a regular distribution of the outcomes int eh long run
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