Y13 RESEARCH METHODS - choosing a statistical test Flashcards
what is a statistical test?
- used to determine whether a significance difference or correlation exists and whether null hypothesis should be accepted or rejected.
what are the 3 factors to consider for a statistical test?
- is researcher looking for a difference or a correlation ( look at the wording of the hypothesis)
- experimental design ( repeated/ matched = related
independant = unrelated) - level of measurement ( nominal,ordinal,interval)
what is nominal data?
data represented in categories and is discrete
eg ppl who yes are in one group and ppl who say no are in another group
what is ordinal data?
data is ordered and ranked but the difference between them is not fixed or meaningful
- lacks precision as it is based on subjective opinion and not objective measures
what is interval data?
data is measured on a scale. units of measurement are fixed and equal, and precisely defined. Necessary criterion for the use of parametric tests.
+ better than ordinal = more detailed is preserved as the scores are not converted to ranks
choosing a statistical test
nominal -
test of difference = unrelated ( chi squared)
related ( sign test)
test of association or correlation = chi squared
ordinal -
TOD = unrelated ( mann-whitney)
related ( wilcoxon)
TOA/C = spearman’s rho
interval -
TOD = unrelated t-test
related t- test
TOA/C = pearson’s t
what is the measure of central tendency + dispersion for : nominal, ordinal, interval
nominal - mode, N/a
ordinal - median, range
interval - mean/standard deviation
what is a parametric test?
related test, unrelated test, pearson’s r
- powerful and robust than other tests
- can detect significance within data sets that other tests cannot.
what is the criteria for parametric test?
- data must be interval level
- data drawn from a population that shows a normal distribution for the variable being measured
- homogeneity of variance = set of scores should have similar distribution or spread ( compare SD’s in each condition)
