EBVM Flashcards
this is when ALL animals in a population are examined to find something out about the population
Census
this is when SOME of the animals in a population are examined to find something out about the population
sample survey
this refers to the entire group of interest in a survey (‘all cows in UK’)
target population
this refers to the animals we can (if we wish) include in a survey
study population
this refers to the ‘thing’ we are surveying
sampling unit
this is the list of all the animals in a study population
sampling frame
this is a sample where we choose which individuals to include
non-probability sampling
this is when we choose individuals for a survey because it is convenient (biased - not a goof representation of the population)
convenience sampling
this is when we choose individuals for a survey, but try to represent the population (good theory but still biased)
purposive sampling
this gives a deliberately unbiased and random sample
purposive sampling
this is when a sampling frame is made and a random subset is selected
simple random sampling
this is when there is no list of all individuals in a sampling frame available, so you create clusters, randomly select some clusters, then create a list of animals in the cluster and randomly sample some of them (less precise)
cluster sampling
this is when characteristics of a population that might be important are identified, then random samples are taken from the groups with the characteristic in proportion to their occurrence in the population (more precise)
stratified sampling
this refers to the ability of a survey to detect effects/relationships present
power
this is a range of values within which we are confident that the true population value lies (usual at a 95% level)
confidence interval
the sample size required for surveys demonstrating disease freedom depends on this
endemic prevalence
this scale of measurement is unordered categories (eye color, sex, religion, etc)
nominal
this scale of measurement is ordered categories (small -> medium -> large)
ordinal
this scale of measurement is counts of things, round numbers only
discrete
this scale of measurement is a numerical scale, fractions are allowed
continuous
this type of continuous data is where 0 is arbitrary (temp - 0C is 32F)
interval data
this type of continuous data is where 0 means nothing/none (weight)
ratio data
this is the chance of seeing the effect we saw in trial data if the null hypothesis was true
p-value
if the p-value is – the null must —
low, go
this type of error is when we conclude there is a difference when there is not one (reject a true null hypothesis)
type 1 error
this type of error is when we fail to spot a difference that is really there (fail to reject a false null hypothesis)
type 2 error
sample size and power of a study are (negatively or positively?) correlated
positively (bigger sample size = higher power)
effect size and power of a study are (negatively or positively?) correlated
positively (bigger effect = greater power)
individual variation and power of a study are (negatively or positively?) correlated
negatively (more indiv variation = less power)
this type of study does not change anything in the animals they study; rely on variation in treatment and risk factor exposures that occur naturally
observational study
this type of observational study is when a random sample of animals is taken at one time simultaneously assessing exposure to risk factor so prevalence of disease can be estimated in each group
cross-sectional study
if the prevalence ratio = 1, this suggests …
no association of disease occurrence with risk factor
if the prevalence ratio < 1, this suggests…
animals w/ exposure to risk factor are less likely to have disease
if the prevalence ratio > 1, this suggests …
animals w/ exposure to risk factor are more likely to have disease
this type of observational study classifies individuals from a random population sample into unexposed and exposed to a risk factor, then follows individuals over a period of time and records any developing disease
cohort study
this is the measure of new cases of disease and can be estimated from cohort studies
incidence
this is the proportion of healthy animals that become ill during the period of study in a cohort study
cumulative incidence
this is the ratio of cumulative incidence in exposed group to control group
relative risk
if relative risk > 1, this suggests…
exposure is associated with increased disease risk
if relative risk < 1, this suggests…
exposure is associated with decreased disease risk
this type of observational study is for rare diseases and asks to be informed about cases if a disease, then presence/absence of a putative risk factor is compared
case-control study
these tell us the strength of association between a risk factor and disease
measures of association (prevalence ratio, relative risk, odds ratio)
this shows us the chance of seeing an association we observed between a risk factor and disease IF there is really no association (null hypothesis is true) - helps make sure we are not fooled by chance
statistical hypothesis test
this is when 2+ risk factors together have a different effect of disease risk than what we would expect from knowledge of individual effects
interaction
this is when the effects of exposure on a given outcome are mixed with effects if an additional factor resulting in distortion of true relationship
confounding
this type of study is when we manipulate treatment of individuals to assess the efficacy of a treatment
clinical trial
this type of clinical trial is when therapy is given to some animals and the outcomes are assessed
uncontrolled trial
this type of clinical trial compares outcomes in a treated group with another group
controlled trial
this type of controlled clinical trial compares the treatment group with parallel control group at same time
concurrent control group
this type of controlled clinical trial compares treatment group with control group in past, possibly from another study
historic control group
this type of control group is untreated
negative control
this type of control group is given a known, effective treatment
positive control
this type of control group is given a substance/therapy with no known therapeutic effect
placebo control
this is when the patient/owner doesn’t know which group they’re in, done to prevent bias
single blinding
this is when the patient/owner AND investigator/vet doesn’t know which groups are which, done to prevent bias
double blinding
this type of clinical trial compares treatment groups to a control group, quick and satisfactory
simple trial
this type of clinical trial compares a treatment group to a control group for a period of time then swaps the groups, finer and more sensitive/powerful
cross-over trial
this type of clinical trial randomly allocates patients to treatment or control group when they are identified with the disease then progress is monitored
sequential trial
this is reported as the etiological fraction and is the prevalence reduction in vaccinated vs unvaccinated animals divided by the prevalence in unvaccinated animals
vaccinal efficacy
this is reported as reduction in parasite numbers between untreated and treated animals divided by the parasite numbers in untreated animals
ectoparasite efficacy
