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31 Cards in this Set
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paired ttest

technique for determining if differences exist between two dependentbased means


What does the one sample ztest and the one sample ttest determine?

if our 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 ttest


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 ttest


What is the null hypothesis for the paired ttest?

u1=u2 There is no significant difference in performance within the two conditions


What does the r in the paired ttest 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 ztest used?

when the sample data has a perfect normal distribution


What does the one sample ztest and the one sample ttest determine?

if the sample mean is significantly different from the population mean


When could the ztest be used?

when all sample data had perfect normal distributions


t distribution

series of approximations of the normal curve for different sample sizes


independent ttest, twosample ttest, Student's ttest

comparing 2 sample means rather than a sample mean to a population mean


What makes up the independent variable in a independent ttest?

there is 1 IV with 2 levels: the 2 different groups that constitute you samples


What are the assumptions of the independent ttest.

randomness, normality, interval/ratio data, 2 independent groups, 10 or more participants per group, homogeneity of variance


What independent ttest 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 ttest?

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 ttest?

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 ttest 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?

zscore


zscores

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 zscores.


What must be known before raw scores can be reported as zscores?

mean and standard deviation


The equations for calculating what is used by most stats programs based on z scores?

skewness
