evidence based Flashcards
evidence based treatment
refers to the interventions or techniques (cognitive therapy for depression etc) that have produced therapeutic change in controlled trials.
evidence based practice
broader term and refers to clinical practice that is informed by evidence about interventions, clinical expertise and patient needs, values and preferences and their integration in decision making about individual care
t-test
differente between sample means memory between walkers and sitters.
assumptions t test
variance in memory does not differ between groups (homoscedasticity), participants are independent of each other (not siblings, same housing group), memory (dep. var.) is normally distributed within groups
general linear model y(i)=b0+b1*x(i)
y= dependent variable b0= indep. var. 1 b1= different dep. var. 1 en 2
assumptions regression analysis
variances equal for all values of x, participants were independent of each other, residuals normally distributed
anova, assumptions
= can be used to test between and within subjects variables
1) variances equal in all groups
2) participants independent of each other
3) data normally distributed within groups
ancova, 2 main goals
1) correct for non-random allocation
2) reduce variance within groups (by taking into acc co-variance with a third variable), promotes power to reject H0 if H0 is really false
ancova, assumpties
1) variances equal in all groups
2) participants independent of each other
3) data normally distributed within groups
4) parallel regression lines (effect of SES on memory equal for sitters and walkers)
repeated measurements analysis assumptions
1) variances equal in all groups
2) participants independent of each other
3) data normally distributed within groups
4) sphericity (univariate approach only) (the variances of the differences between all possible pairs of within-subject conditions are equal)
multiple comparison problem
for type 1 error, if you apply 100 tests together they stand a much higher chance of false positives
power
correcte rejecting the null hypothesis (1-Beta) / , researchers consider a study to be adequately powered if it has at least an 80% chance of detecting a clini- cally significant effect when one ex- ists.
beta
type 2 error, false negative,
effect size
Effect size is a quantitative measure of the magnitude of the experimental effec// the degree of non-overlap between sample distributions (the less overlap the larger the effect size), the probability that one could guess which group a person came from, based only on their test score (effect size d=0 -> correct guess 0.5, d=1 prob rises to acceptable levels)
effect sizes for discrete variables
Cohens d, hedges g, Pearson correlation r
odds ratio
an effect size for discrete outcomes
meta regression
to get a summary of the literature
disadvantages narrative review
focus on p-values in original studies
tempration t write things that still support your theory
how to deal with studies that differ in reliability?
often based only on published literature (file drawer)
interpretation of intercept
the value. you expect if you score zero on all independent variables
r
strengst of association between variables
d
magnitude of the difference between treatment and comparison groups
NNT(needed to treat)
the number of patients who must be treated to generate one more success or one less failure than would have resulted had all persons been given the comparisons treatment
AUC (area under the curve)
represents the probability that a randomly selected subject in the treatment group has a better result than one in the comparison group
statistical power
is the conditional probability that a true effect of a precisely specified size in the population will be detected in a study using such conventional significance testing
underpowered studies
- provide insufficiently meaningful information - add to replicability problems (higher prob of false positives/negatives - are a waste of (vulnerable) clients (& everyone else’s) time
overpowered studies
- unnecessarily exposing participants to an intervention that may not work or may have side effects - are a waste of resources - (although we really want high power!)
moderation
moderators affect the effect of treatment// example : the strength of the relationship between game playing and aggression is affected by callous unemotional traits (moderator) // treatment effect depends on variables that are themselves independent of treatment (sex; nominal moderator, intelligence; continuous moderator)
mediation
mediation is said to have occurred if the strength of the relationship between the predictor and outcome is reduced by including the mediator// mediators are affected by treatment//which processes are important during an intervention? (what mechanisms underlie intervention effects) (sleep problems; nominal mediator, hours of sleep ; continuos mediator)
logistic regression
regressing a dichotomous dependent variable on the basis of on or more (nominal or continuous) independent variables
with logistic regression you can do enter or stepwise
enter = keep all independent variables in model (test an explicit hypothesis : confirmatory) or stepwise forward/backward = let sass find out which variables are important (no explicit hypothesis : exploratory)