statistical tests

why would you use man whitney U

randking ordinal data, no fixed intervals between the data, looking at the median and range

what is the statement of significance for man whitney u

P< 0.05, critical value must be larger than observed value

when do you use non-parametric tests

comparing medians, unusual distributions, ordinal data e.g. man whitney u, spearman ro, wilcoxon sign test

what is the statement of significance for wilcoxon

p<0.05 the calculated value must be equal to or less than the critical value to have significance

variance

helps psychologists understand how spread out the data is, low variance = scores close to the mean, high variance = score more spread out, average squared distance from the mean

standard deviation

average actual distance from the mean, easier to interpret, more useful than range as it takes all the scores into account and is the square root of the variance

when do you use a parametric test

data is interval, data is normally distributed( 68% of data should be less than ± than standard deviation) , comparing means and variance between groups are approximately equal

why would you use spearman’s rho

when looking at the ranks of the data when there is no equal interval, looking for a correlation

statement of significance for spearman’s rho

the observed value must be larger or equal to the critical value

when would you use chi sqaured

when you’re looking for a relationship, data is ordinal or interval,

what is the binomial test and when do you use it

looks for a difference between two related conditions, when the data is nominal, based on whether participants did better or worse or the same in one condition compared to another nominal, repeated measures

what are normal distribution curves

when the curve is symmetrical on both sides and the median and mode are similar to the mean

which tests is significant when the observed value is less than

wilcoxon, man whitney u and sign test

which tests are significant when the observed value is larger than

chi sqaured, spearman rho

negative skew

when the mean is lower than the the median and mode due to anomalous data the tail of the curve i dragged out to the left

positive skew

the mean is higher than the median and mode and the tail of the curve is dragged to the right