Statistics Flashcards
what do inferential statistics allow to?
allow to generalize from the sample to the population, which the sample represents
why are inferential statistics crucial?
are crucial because the effects that researchers find in a study may be due to random variability caused by sampling error
what are the variables in experimental research?
independent variable and dependent variable
what is the independent variable?
The variable that is manipulated (e.g. a treatment).
-> continuous
what is the dependent variable?
The variable that is measured (e.g. the outcome of a treatment)
-> Continuous or discrete/categorical
what is the relationship between IV and DV?
IV -> DV
what is hypothesis testing?
a statistical inference procedure for determining whether a given proposition about a population parameter should be rejected on the basis of observed sample data
what is the goal of hypothesis testing?
goal of hypothesis testing is to make inferences about a population based on a sample
what is the null hypothesis?
there is no difference in the population(H0)
what is it called when you incorrectly reject the null hypothesis?
type I error
what is in called when you incorrectly fail to reject the null hypothesis?
type II error
what is the alternative hypothesis?
there is a difference in the population (Ha)
what are the types of alternative hypotheses?
Directional alternative hypothesis
Non-directional alternative hypothesis
what is the Non-directional alternative hypothesis?
The direction of the effect is not determined
Delayed reward leads to either slower or faster learning
what is the Directional alternative hypothesis?
The direction of the effect is determined
Delayed reward leads to slower learning
what are the potential outcomes of hypothesis testing?
reject the null hypothesis
fail to reject the null hypothesis
what does rejecting the null hypothesis not mean?
that the alternative hypothesis is true
* The alternative hypothesis (H1) is never proven true in an absolute sense
* It is only demonstrated that the null hypothesis is very unlikely given the data
what does failing to reject the null hypothesis not mean?
This does not mean that the null hypothesis is true but only that evidence against the null hypothesis is not convincing enough to reject it
what are the steps for hypothesis testing?
1) state the hypothesis
2) set the criteria for a decision
3) compute the test statistic
4) make a decision
what is the level of significance?
refers to a criterion of judgment upon which a decision is made regarding the value stated in a null hypothesis. The criterion is based on the probability of obtaining a statistic measured in a sample if the value stated in the null hypothesis were true.
what does the significance level represent?
the maximum acceptable probability of rejecting a true null hypothesis (type I error)
what % is the significance level in psychology usually?
5% or 1%
The significance level determines how … one is to reject the null-hypothesis
conservative
If one has a non-directional hypothesis one needs to carry out a …
two-failed test
what is the test statistic?
is a mathematical formula that allows researchers to determine the likelihood of obtaining sample outcomes if the null hypothesis were true
what is the value of a test statistic used for?
to make a decision regarding the null hypothesis
what is the decision based on?
the probability of obtaining a sample mean, given that the value stated in the null hypothesis is true
what is the decision when the probability of obtaining a sample mean is less than the significance level?
decision is to reject the null hypothesis
what is the decision when the probability of obtaining a sample mean is greater than the significance level?
decision is to retain the null hypothesis
(1- α)
The decision to retain the null hypothesis could be correct
(α)
The decision to reject the null hypothesis could be incorrect
(β)
The decision to retain the null hypothesis could be incorrect
(1- β)
The decision to reject the null hypothesis could be correct
which error is it when the decision to reject the null hypothesis could be incorrect
type I error (α)
which error is it when the decision to retain the null hypothesis could be incorrect
type II error (β)
what is type I error?
probability of rejecting a null hypothesis that is actually true
what are the consequences of type I error?
Type I can be bad, because it might mislead researchers to believe that a manipulation or treatment is effective while in fact it is not
what is type II error?
the probability of retaining a false null hypothesis
what are the consequences of type II error?
Type II may not be so bad, if it is understood that the manipulation or treatment may still have an effect (we fail to reject the null hypothesis, but we do not reject the alternative hypothesis)
what is the power in hypothesis testing?
the probability of rejecting a false null hypothesis
what is (1-ß)?
statistical power
what is the power of a hypothesis test denied as?
the probability that the test will reject the null hypothesis when the treatment does have an effect (rule of thumb: minimum of 80%)
what does statistical power depend on?
effect size
alpha level
sample size
which effect size means more power?
larger effect size
which alpa level means more power?
liberal alpha level
which sample size means more power?
larger sample size
