statistical testing Flashcards
define statistical testing
- provides a way of determining whether hypotheses should be accepted or rejected
- they tell us whether differences or relationships between variables are statically significant OR have occurred by chance
why do we need to complete a statistical test ?
to see whether the difference found within studies haven’t occurred by chance/coincidence
define sign test
a statistical test used to analyse the difference in scores between related items
what is an example of ‘related items’ ?
the same participant tested twice
what are the 2 types of hypotheses ?
- the original/alternate hypothesis
- the null hypothesis
what is the difference between original and null hypothesis ?
O - states there will be an effect
N - states there will not be an effect
give an example of original hypothesis
there will be a difference in participants depression score on the BDI before and after a 6-week course of CBT
give an example of null hypothesis
there will be no difference in participants depression score on the BDI before and after a 6-week course of CBT
what are the abbreviated form of original and null hypothesis ?
H1 - O
H0 - N
what does the statistical test allow to decide between original and null hypothesis ?
to determine whether to accept or reject the null hypothesis
what is the sign test used for ?
used to find out whether the difference established is significant
what conditions need to be met in order to carry out the sign test ?
- looking for a difference rather than an association
- have used a repeated measures design
- nominal data.
what are significance levels used for ?
to check for significance differences or relationships
what is the accepted level of probability in psychology ?
0.05 / 5%
define significance levels
represents the threshold at which researchers decide whether to reject the null hypothesis
what does it mean if the experimental hypothesis is accepted ?
this means there is less than 5%
probability that the results occurred by chance
what do some researchers do to the significance level and why ?
-make a stringent (small) signifance level (0.01/1%)
- means that researchers can be more confident in their results
- to make sure that results weren’t due to a chance
give examples of why one may want to employ 1% level of significance
- may involve a human cost (new drugs are being on trial )
- when a particular investigation is a one-off , and there is no possibility that it can be repeated in the future
what can choosing the wrong significance levels result in ?
type 1 error + type 2 error
define type 1 error
if too lenient significance level is used
(e.g. 10% )
–> results rejecting the null hypothesis that is fact true
null hyp = true
alt hyp = wrong
define type 2 error
if a too stringent significance level is used
(e.g. 1%)
–> results in accepting a false null hypothesis
null hyp = wrong
alt hyp = true
what does one -tailed and two-tailed mean ?
one-tailed means directional hypothesis
two-tailed means non-directional hypothesis
what are 5 pieces of information one needs in order to reading a table of critical values
- the significance level desired (always 0.05 or 5% except in the cases described
above). - the number of participants in the investigation (the N value),
- whether the hypothesis is directional (one-tailed) or non-directional (two-tailed)
- the calculated value
- the critical value
what does test of difference/correlation mean ?
association or relationship = correlation
