week 5: stats tests i did at a level

is this a foundation year. i swear to god.

t tests:

• examine differences between groups of people

  • compare distributions of groups - central tendency and variability

• shows us whether there is a statistically significant difference between two groups

• data needs to meet assumptions:

  • normal distribution

  • interval/ratio data

  • homogeneity of variance = data sets are spread out the same amount

    • tested via levene’s test - significant test = no homogeneity of variance

  • no extreme data scores

• parametric

  • non parametric equivalent = wilcoxon test for repeated measures, mann whitney for independent

• see slides for actual equation but the components are:

  • difference between means of sample (m1-m2)

  • variability of data in samples (sd1 and sd2)

  • sample sizes (n1 and n2)

• 2 types of t test:

  • independent measures = used for independent groups design - data from 2 different groups

  • repeated measures/paired samples = ppts are assessed twice and give two sets of scores

mann whitney:

• assumptions:

  • non parametric data

  • comparing 2 groups

  • independent groups

• if you really want to know how jamovi does it for you see slides

wilcoxon signed rank:

• assumptions:

  • non parametric data

  • comparing 2 groups

  • repeated measures

• again there’s a slide of useless information about how software does it for you

pros and cons of non parametric:

pros:

• do not rely on restrictive parametric assumptions

• unaffected by outliers

cons:

• less powerful than parametric

• more observations needed for this than parametric to find significance

  • not as good for smaller samples

standard error:

• shows us how accurately our sample represents the population

• standard deviation over square root of number of people in the sample

• estimated standard deviation for the central tendency of an infinite population

• small se indicates representative sample

if you need a refresher on critical value tables give your head a wobble but they’re in there