probability & significance Flashcards
what do researchers begin their investigations by doing
writing either a directional or non-directional hypothesis (alternative hypothesis)
what does the null hypothesis state
there is no difference between the conditions
what does the statistical test determine
which hypothesis is ‘true’ and if we accept/reject the null hypothesis
what do all statistical tests employ
a significance level = point at which the researcher can claim to have discovered a large enough difference/correlation within the data to claim an effect has been found
(reject null hypothesis & accept the alternative hypothesis)
what is the usual level of significance in psychology
0.05 (5%)
what is the calculated value
once a statistical test has been calculated, the result is a number (calculated value)
what must the calculated value be compared with to check for statistical significance
critical value = tells us whether we can reject null hypothesis & accept alternative hypothesis
3 criteria to know which critical value to use
- one-tailed (directional hypothesis) or two-tailed test (non-directional hypothesis)
- number of participants in study
- level of significance
define one-tailed & two-tailed hypothesis
one-tailed = directional hypothesis
two-tailed = non-directional hypothesis
define type I error
- null hypothesis rejected & alternative hypothesis accepted when it should have been the opposite way round
- optimistic error/false positive
- researcher claims to have found significant difference/correlation when there isn’t one
define type II error
- null hypothesis accepted but alternative hypothesis should have been accepted
- pessimistic error/false negative
when are type I and type II errors most likely
- type I error likely if significance level is too high
- type II error most likely if significance level is too low
