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Quantitative Methods
Final Exam
31
Psychology
Undergraduate 2
04/20/2009

Additional Psychology Flashcards

 


 

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Term
1 - alpha
Definition
the probability of correctly failing the null hypothesis when there is no effect
Term
1 - beta
Definition
the power of an experiment, the probability of correctly rejecting the null hypothesis where there is an effect
Term
Type 1 error = alpha
Definition
rejecting the null hypothesis incorrectly
Term
Type II error = beta
Definition
retaining null hypothesis incorrectly
Term
How to control alpha?
Definition
setting it at .05, .01 or less
Term
How to control beta?
Definition
our assumptions about how much of a difference might exist in the world is referred to as the EFFECT SIZE, assuming different effect sizes can show how much power our study has, allowing us to better evaluate the failure to reject the null hypothesis
Term
Power
Definition
the proportion of the distribution under p-real that falls into the rejection region for the null hypothesis (p-null)
Term
p-real
Definition
a probability of success that represents the effect size (the true difference in the world)
Term
p-null
Definition
the probability of success under the null hypothesis (almost always 0.5)
Term
Central Limit Theorem
Definition
when a variable is influenced by many small independent factors, its distribution will approach the normal distribution as the size of the sample increases
Term
Sampling
Definition
Have a population, draw a sample of size N, calculate a statistic on that sample, repeat the process over and over, this describes the values of the statistic and how often these values occur, the distribution of the statistic depends on the characteristic of the underlying population and the sample size (N)
Term
Hypothesis testing
Definition
obtain a date sample, calculate a test statistic, understand the sampling distribution of the test statistic under the null hypothesis, use this understanding to identify critical values, test the likelihood of getting the observed sample under the null hypothesis by comparing the test statistic to the critical values, reject or fail to reject the null hypothesis
Term
Z-test
Definition
used when the mean and standard deviation of the population, specify the sampling distribution of the mean for your sample size, draw sample, test hypothesis the mean could have occurred by chance given the null hypothesis
Term
degrees of freedom (df)
Definition
the number of scores that are free to vary in calculating that statistic (Mean has N df, standard deviation has N-1 df)
Term
t-test
Definition
developed to be used when the standard deviation has to be estimated from the sample
Term
Cohen's d
Definition
absolute value of the difference between sample and population mean in standard deviation units
Term
Different uses of statistics
Definition
Descriptive, Hypothesis testing, size or effect, point estimation
Term
Confidence Intervals
Definition
quantify the degree of accuracy or precision of a point estimate, values that bound the upper and lower end of the confidence interval are confidence limits
Term
Three applications of t-test
Definition
t-test for a single sample, t-test for correlated samples, t-test for independent groups
Term
t-test for a single sample
Definition
compare a mean to a hypothesized value
Term
t-test for correlated samples
Definition
compare means when the data is paired within subjects (pre-post) or between subjects (matched pairs)
Term
t-test for independent groups
Definition
compare means between two groups formed by experimental (random assignment) or observational (e.g., gender) independent variables
Term
F-distribution
Definition
sampling distribution of the ratio of two variances
Term
F-ratio
Definition
the between groups variance divided by the within groups variance
Term
a priori comparison
Definition
you need not correct alpha for multiple comparisons, typically only make a few critical comparisons, compare each pair of means using t-test, the within groups variance is the best estimate of the variance to use in estimating the standard error of the difference between two means
Term
Post Hoc comparisons
Definition
you should adjust the alpha level for multiple comparisons, experiment-wise error rate (control your hypothesis testing so that the error rate given all post hoc tests is alpha), comparison-wise error rate (control multiple comparisons by adjusting the comparison wise error rate (alpha is set for each comparisons))
Term
within group variance
Definition
pooled estimate based on the variability around the group mean within each group
Term
between group variance
Definition
variance of the group means around the grand mean
Term
Power changes
Definition
increases with N, increases with effect size (greater differences between the group means), decreases as the population variance increases
Term
Interaction effect
Definition
occurs when the effect of one factor is not the same at all levels of the other factor
Term
chi-square
Definition
x2, asymmetric distribution, df is (r-1)(c-1), used for hypothesis testing, only do non-directional alternative hypothesis except when df=1, considered a two-tailed, non directional test
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