week 9 pt. 2 Flashcards
whats the difference between descriptive and inferential statistics
descriptive: organises and summarises data (central tendency, variability)
inferential: using sample data to draw conclusion about population (confidence interval, t test, person r, etc)
whats the relationship between sample size and effect size
sample size: larger sample will have a small effect
effect size: smaller sample will be able to detect a large effect
what is the relationship with alpha value and p value
you look at alpha value and relate it to p value to see if things are significant
what is a confidence interval
you have a survey where 60% of people like pizza, with a confidence interval of 55-65% (where the real answer lies)
this means you’re 95% confident that the answer is between 55-65%
what are t tests
way to compare the difference between two means
what are t tests with independent groups
compares 2 separate groups to see if their means are different
i.e. men and women and their average alcohol consumption
what are t test with dependent groups
compares 2 related groups or measures the same group at diff times
ex. average weight for ppl before and after a fitness program
what is person r
shows how strong relationship is between two things
positive R: one goes up, the other goes up
negative r: perfect negative relationships one goes up the other goes down
r= 0, no relationship
in a study where hours spend studying compared to test scores with an r= 0.9
what does this mean
strong positive correlation with increased studying resulting in increased test scores
what are threats to internal validity
bias, attrition, contamination, Hawthorne
what are threats to external validity
inadequate sample size, inability to generalise
what is type 1 error
null hypothesis is rejected even when its true (false positive)
what is a type 2 error
null hypothesis is accepted even when its false (false negative)
