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Statistics
Exam 2 - Chapters 6-10
45
Social Work
Undergraduate 3
11/09/2011

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Term
Central Limit Theorem
Definition

A theorem that specifies the mean, standard deviation, and shape of the sampling distribution, given that the sample is large.

n>100

Term
Cluster Sample
Definition
A method of sampling by which geographical units are randomly selected and all cases within each selected unit are tested.
Term
E.P.S.E.M
Definition
The Equal Probability of SElection Method for selecting samples.  Every element of case in the population must have an equal probability of selection for the sample.
Term
μ - mu
Definition
The mean of a population
Term
μ -sub- X_ (mu sub mean)
Definition
The mean of a sampling distribution of sample means.
Term
μ -sub- p
Definition
The mean of a sampling distribution of sample proportions.
Term
P -sub- s
Definition
Any sample proportion
Term
P -sub- u
Definition
Any population proportion
Term
Representative
Definition
The quality a sample is said to have if it reproduces the major characteristics of the population from which it was drawn.
Term
Sampling Distribution
Definition

The distribution of a statistic for all possible sample outcomes of a vertain size.

Under conditions specified in two theorems, the sampling distribution will be normal in shape, with a mean equal to the population value and a standard deviation equal to the population standard deviation divided by the square root of N.

Term
Simple random sample
Definition
A method for choosing cases from a population by which every case and every combination of cases has an equal chance of being included.
Term
Standard error of the mean
Definition
The standard deviation of a sampling distribution of sample means.
Term
Stratified Sample
Definition
A method of sampling by which cases are selected from sublists of the population.
Term
Systematic Sampling
Definition
A method of sampling by which the first case from a list of the population is randomly selected.  Thereafter, every kth case is selected.
Term
Alpha
Definition
The probability of error, or the probability that a confidence interval does not contain the population value.  Alpha levels are usually set at 0.10, 0.05
Term
Bias
Definition
A criterion used to select sample statistics as estimators.  A statistic is unbiased if the mean of its sampling distribution is equal to the population value of interest.
Term
Confidence Interval
Definition
An estimate of a population value in which a range of values is specified.
Term
Confidence Level
Definition
A frequently used alternate way of expressing alpha, the probability that an interval estimate will not contain the population value.  Confidence Levels of 90%, 95% correspond to alphas of 0.10 and 0.05.
Term
Efficiency
Definition
The extent to which the sample outcomes are clustered around the mean of the sampling distribution.
Term
Point Estimate
Definition
An estimate of a population value where a single value is specified.
Term
Alpha Level (2)
Definition
The proportion of area under the sampling distribution that contains unlikely sample outcomes, given the null hypothesis is true, it is the probability of Type 1 error
Term
Critical Region (region of rejection)
Definition
The area under the sampling distribution that, in advance of the test itself, is defined as including unlikely sample outcomes, given that the null hypothesis is true.
Term

Six Step Model

 

Definition

1-make assumptions

2-null and research hypothesis

3-draw picture

4-state alpha, df, and t or z critical

5- compute equation

6-findings

Term
Hypothesis Testing
Definition
Statistical tests that estimate the probability of sample outcomes if assumptions about the population (null hypothesis) are true.
Term
Null Hypothesis (HsubO)
Definition
A statement of "no difference" in the context of single sample tests of significanece, the population from which the sample was drawn is assumed to have a certain characteristic or value.
Term
One-Tailed Test
Definition
A type of hypothesis test used when 1- the direction of the difference can be predicted or 2- concern focuses on outcomes in only one tail of the sampling distribution
Term
Research Hypothesis (Hsub1)
Definition
A statement that contradicts the null hypothesis.  In the context of single sample tests of significance, the research hypothesis says the population from which the sample was drawn does not have a certain characteristic or value
Term
Student's t Distribution
Definition
A distribution used to find the critical region for tests of sample means when σ is unknown and sample size is small.
Term
t(critical)
Definition
The t score that marks the beginning of the critical region of a t distribution
Term
t(obtained)
Definition
The test statistic computed in step 5 of the six-step model.  The sample outcome into either a t score or a z score.
Term
Test statistic
Definition
The value computed in step 5 of the 6 step model that converts the sample outcome into either a t or z score.
Term
Two tailed Test
Definition
a type of hypothesis test used when 1 the direction of the difference cannot be predicted or 2 concerns focus on outcomes in both tails of the sampling distribution.
Term

Type 1 and Type 2 Errors

Alpha and Beta

Definition

Alpha Error- the probability of rejecting a null hypothesis that is, in fact, false.

Beta Error- The probability of failing to reject a null hypothesis that is, in fact, false.

Term
Independent Random Samples
Definition
Random samples gathered in such a way that the selection of a particular case for one sample has no effect on the probability that any other particular case will be selected for the other samples.
Term
Pooled Estimate
Definition
An estimate of the standard deviation of the sampling distribution of the difference in sample means based on the standard deviation of both samples.
Term
σp-p
Definition
symbol for the standard deviation of the sampling distribution of the differences in sample proportions.
Term
σx-x
Definition
symbol for the standard deviation of the sampling distribution of the differences in sample means
Term
Analysis of Variance
Definition

A test of significance appropriate for situations in which we are concerened with the differences among more than two sample means.

 

Term
ANOVA
Definition
Analysis of Variance
Term
F ratio
Definition
The test statistic computed in step 5 of the ANOVA test
Term
One-Way Analysis of Variance
Definition
Applications of ANOVA in which the effect of a single independent variable on a dependent variable is observed.
Term
Post Hoc Test
Definition
A technique for determining which pairs of means are significantly different
Term
Sum of Squares Between (SSB)
Definition
The sum of the squared deviations of the sample means from the overall mean, weighted by sample size
Term
Sum of Squares Within (SSW)
Definition
The sum of the squared deviations of scores from the category means
Term
Total Sum of Squares (SST)
Definition
The sum of the squared deviations of teh scores from the overall mean.
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