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Study guide for exam 3
Chapters 7 and 8
Psychology 230  Statistics
Spring, 2008
Hypothesis testing with z, and t scores
Describe the logic of when we reject the null hypothesis
↵
What is the relationship between the observed statistic and critical
statistic?

Describe the similarities and differences between the z and t
sampling distributions
Both benefit from the central limit theorem truly random influences and a large
number of influences combined make a normal curve. As N becomes larger, the
distribution of sample means approaches normality, with the overall mean
approaching the theoretical population mean.
both are bell shaped and symmetrical so we can complete one or two
tailed tests
both z and t have a mean of zero
the shape of the t sampling distribution is very sensitive to small sample
sizes, so we need df to find regions of the curve (and scores)
be able to find critical tscores on the table on page 671
How does the variability change in a tdistribution as the sample size increases?
Larger sample less variability
What is a point estimate?
Describe the pros and cons relative to confidence intervals
Point estimates are a more specific estimation, but less likely to be exactly
right
Confidence intervals are more general (range of scores), but more likely to
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This note was uploaded on 05/08/2008 for the course PSYC 230 taught by Professor Delaney during the Spring '08 term at University of Arizona Tucson.
 Spring '08
 Delaney
 Psychology

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