Chapter 9: T-statistics Flashcards
why do we use the t-statistic?
The t statistic doesn’t require any knowledge of the population standard deviation
what is the purpose of the t-statistic?
use sample data to test hypotheses about an unknown population mean
estimated standard error
Sm= s/√n
t-statistic formula
t= M-μ/ Sm
t-distribution
Family of distributions, one for each value of degrees of freedom
t-distribution vs. z-distribution
Flatter than the normal distribution
More spread out than the normal distribution
More variability (fatter tails) in the t distribution
columns of the z-distribution table
organized by a levels with common decisions rules listed
rows of the z-distribution table
for different sample sizes and the associated degrees of freedom
z-score vs t-score
The t statistic is like an estimated z score
hypothesis testing procedure for t-scores
Same four-step procedure as for z-scores
assumptions of the t-test
The values of the sample must consist of independent observations
The population that is sampled must be normal
estimated cohen’s d formula
Estimated d= M-μ/s
what is a small effect
r²= 0.01
what is a medium effect
r²= 0.09
what is a large effect
r²= 0.25
