# Statistics Exam 2

## Terms

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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?
- z-score
- z-scores
- 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?
- skewness