Quick Review: Test 2 Flashcards
(37 cards)
What is the sampling distribution?
The distribution of a statistic over repeated sampling
What is sampling error?
the variability of sample estimates of some statistic such as the mean
What is the standard error of the mean?
the standard deviation of the sampling distribution of the mean
What do we mean by hypotheses testing?
We are referring to testing some hypothesis about the relationships between population parameters
What is a research hypothesis?
this is the hypothesis that there is a true difference or a true relationships between the variables
What is the null hypothesis?
the hypotheses that is apparent difference difference or relationship is due to change
- Saying things dont affect eachother
example: going through cognitive therapy does not affect an anorexic girls weight
Why do we test null?
the alternative hypothesis is to vague, where as the null hypotheses is specific and if we can reject it, we can argue that the alternative hypothesis is true
what is another term for rejection level?
the significance level
What is a type II error?
rejecting the null hypothesis, when the null hypothesis was actually true (false negative)
What is a critical value?
the value of the test statistic beyond which you reject the null hypotheseis
We often reject the null if the conditonal probabibility of the data, given tthat the null is tue, is less then .05? what symbol do we use to represent this?
alpha
if we reject the null only if the difference betweel the groups is POSITVE, we are using whwat kind of tailed test?
1 tailed
-because we are explaining one specific direction
List three things the central limit theorum tells us:
- the mean equals the population mean
- the standard deviation (standard error) equals the population standard deviation divde by the square root of n
- The distrubition approaches normal as N increases
why do we care about the standard error of a statistic?
it tells us how variable that statistic is over repeated sampling
What does formula for t differ from the formula for z ?
we replace Z raw score of (x), into t scores with a statistic of a sample (Mean)- and we replace population standard deviation, with the standard error of the mean
Why is the sampling distribution of the variance relevant for t tests?
the sampling distribution is positively skewed, especially for small samples, so any particular sample standard deviation is more likely to underestimate the population standard deviation, then over estimate it
when we are dealing one set of scores, what will the degree of freedom be?
n-1
name three things that affect the size of the t we calculate
the size of the difference, the size of the variance and the sample size
what do we mean when we speak of an effect size measure?
we refer to some measure that tells about how large a difference is, in a meaningful metric rather then weather or not its statisticaly signficant
what is the confidence interval
we are speaking about an interval that is calculated in such a way that it has a partciular probability (95%), of including the true population value of a parameter
What does cohens effect measure?
(d)
it is a measure of how far the sample mean differs from a population mean when expressed in terms of standard deviations
what is sampling distribution of t?
this is the distribution that the t statistic would take on over repeated sample if the null hypotheses was true
What do we mean by matched samples?
the observations come in pairs, such that the two items in the first row of data come from the same person, or are related in some way
the major advantage to matched samples are”
allow us to remove extraneous variance before calculating t
