Stats Exam 3
repeated measures design two types
pre-post design and within subjects design
advantages for selecting related samples
selecting related samples can be more practical, selecting related samples minimizes standard error, selecting related samples increases power
sample size
standard deviation
type I error
standard error
Explain when it appropriate to use a standard error versus a standard deviation for z scores?
standard error is used in z scores when comparing a sample mean to a population mean. standard deviation is used when comparing a score to a population mean
using estimated standard error less to
t- distribution
power is
the probability of rejecting a false null
what does a value of 0 mean for a cohens d?
the sample mean and population are the same there is no effect
increase sample size decreases standard error
thereby increases power
d(effect size)
type II error
pre-post design
type of repeated measures design in which researchers measure a dependent variable for participants before and following some treatment
within subject design
type of repeated measures design where researchers observe the same participants across many treatments but not necessarily before and after a treatment
In what situation would a researcher want to conduct a one sample t test?
when U is known, o is unknown and the population is normally distributed
medium cohens d
0.2 < d < 0.8
Estimated Cohen's d
A measure of effect size in terms of the number of standard deviations that mean scores shift above or below the population mean stated by the null hypothesis. The larger the value of estimated Cohen's d, the larger the effect in the population
matched pairs design
A method of assigning subjects to groups in which pairs of subjects are first matched on some characteristic and then individually assigned randomly to groups.
estimated standard error
An estimate of the standard deviation of a sampling distribution of sample means with an unknown variance
cohens d
a measure of effect size that assesses the difference between two means in terms of standard deviation, not standard error
repeated measure design
a research design in which the same participants are observed in each sample. the most common related sample design
treatment
any unique characteristic of a sample or any unique way that a researcher treats a sample. can change value of a dependent variable, associated with variability in a study
normality
assume that data in the population being sampled are normally distributed
independence
assume that probabilities of each measured outcome in a study are independent
random sampling
assume that the data were obtained using a random sampling procedure
How is estimated cohens d different than eta squared as a measure of effect size?
cohens d measures the shift in standard deviations above and below the mean. ETA and omega squared measure the amount of variance explained by the variable you manipulated
small cohen's d
d < 0.2
large cohens d
d > 0.8
effect vs effect size
effect is the difference between sample mean & population mean stated in null while effect size is size of a effect in a population
When calculating a two independent sample t? the error term is?
estimated standard error of the mean for the differences
matched pairs design has
experimental manipulation and natural occurrence
participants can be related in two way
in more than one group, are matched
proportion of variance
measure of effect size in terms of the proportion or percent of variability in a dependent variable that can be explained or accounted for by a treatment
degrees of freedom
n-1
two independent sample t test four assumptions are made
normality, random sampling, independence, equal variances
a statistical procedure used to test hypotheses concerning the mean in a single population with a unknown population variance is called?
one sample t test
Why would you use a one versus two tailed test
one tailed are used when you have a predicated direction. two tails are exploratory and more conservative
In a situation where two samples have similar or equivalent variances it is appropriate to?
pool the variances together
to compute a zobt score what must be known
population variance
as effect size increases
power increases