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Statistics Exam 2


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paired t-test
technique for determining if differences exist between two dependent-based means
What does the one sample z-test and the one sample t-test determine?
if the sample mean is significantly different from the population mean
What type of test would be used when pairs of participants are matched on one or more characteristics and randomly placed in two different groups (e.g. experimental and control)
paired t-test
What type of test would be used when twin studies (or siblings) where one twin is in Group 1 and the other is in Group 2
paired t-test
What is the null hypothesis for the paired t-test?
u1=u2 There is no significant difference in performance within the two conditions
What does the r in the paired t-test formula mean?
the correlation between the scores from the 2 dependent samples.
What should the magnitude of the r be for the scores to be considered dependent (i.e. related)
.4 or greater
What is the criteria for rejecting the null hypothesis?
p value is less than or equal to an alpha of .05
When is the z-test used?
when the sample data has a perfect normal distribution
When could the z-test be used?
when all sample data had perfect normal distributions
t distribution
series of approximations of the normal curve for different sample sizes
independent t-test, two-sample t-test, Student's t-test
comparing 2 sample means rather than a sample mean to a population mean
What makes up the independent variable in a independent t-test?
there is 1 IV with 2 levels: the 2 different groups that constitute you samples
What are the assumptions of the independent t-test.
randomness, normality, interval/ratio data, 2 independent groups, 10 or more participants per group, homogeneity of variance
What independent t-test assumption do you not have to worry about if the group sizes are equal?
homogeneity of variance
What do you do if the group sizes are not equal in an independent t-test?
test for the assumption of equal variance
Levene's test
used for testing for equal variance
what do you do if the variances between the gruops are equal in an independent t-test?
You can use a different formula for t that uses a "pooled" or average variance for the groups. This usually results in a lower error term and thus greater power.
When is the effect size used?
before a study to estimate sample size- based on an average effect size from the literature
What does effect sizehelp estimage?
the meaningfulness of your treatment
What can you use to get a better picture of the magnitude of the difference between two means after the study?
effect size
How is the effect size most often used?
to describe the difference between the mean of the experimental group and the control group
omega squared
another way of evaluating effectiveness of treatment
When should omega squared be calculated?
after a t-test if a significant difference is found
What does omega squared indicate?
the proportion of the variance in the dependent variable that is explained by the independent variable
normal distribution
scores on the dependent variable can be expressed as a standard score as a basis of comparison
What is the most common standard score used with a normal distribution?
the standardized score used to produce a normal curve with mean=0 and s=1. It essentially represents a raw score expressed in standard deviation units. Can convert raw scores from a distribution into z-scores.
What must be known before raw scores can be reported as z-scores?
mean and standard deviation
The equations for calculating what is used by most stats programs based on z scores?

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