other Flashcards
precision - aka
accuracy - aka
precision = consistency = reproducibility = reliability accuracy = truness = validity
accuracy vs precision according to errors
accuracy –> systemic
precision –> random (explain by chance - unpredicable)
Metanalysis disadvantage
while it pools together the data from many studies, it also pools together the biases and limitations of those individuals studies
case fatality rate
divide number of fetal cases by the the total number of people with this disease
Hawthorne effect
(aka observer effect) is the tendency of study subjects to change their behavior as a result of their awareness that their being studied
how to minimize Hawthorne effect
study subjects can be kept unaware that they are being studied –> this can occasionally pose ethical problems
Health promotion?
according to WHO –> the process of enabling people to increased control over their health + its determinants and thereby improve their health
examples: dietary habits, exercising regularity, no smoking, lossing weight if needed
FALLS UNDER PRIMARY PREVENTION
Detection bias
the risk factor itself may lead to extensive diagnostic investigation and increase the probability that a disease is identified
Sampling bias
non-random sampling selection
Ecological study
like cross sectional but in populations (not in individuals)
t-test types (explain)
- 2 sample T test –> aka Student’s test –> compare means of 2 independed groups
- Paired T test –> depended –> compare 2 means from the same individuals
Fisher’s exact test
like X square test but in smaller sample
less than 10 people in each cell
anova - types (explain)
- 1 way analysis –> 1 variable (weight loos mean in 3 dif groups)
- 2 ways analysis –> 2 variables (eg. weight loss man in 3 dif groups + men vs women
ROC (receiver operating characteristic) def + expl
graphic with sensitiviy at y + 1-specif (FP rate) at x for a diagnostic test
explanation –> the closer the curve to the diagonia, the less discrimination ability of the test. The closer to the y axis, the better discrimination
variables - types and definition
independent –> an experimenter can change it (salt in diet)
depended –> outcomes that reflex to the change (blood pressure)
counfounding bias strategy of reduction
- multiple repeated studies
- crossover studies
- matching
- restriction
- randomization
- standard deviation vs standard error of a mean (SEM)
- how much variability from the mean in a set of values
2. how much variability exits between the sample mean + the true population
case series studies
descriptive study that tracks patients with a known condition (eg. particular exposure, risk factor, disease) to document natural history or response to treatment (qualifying study that cannot quantify statistical significance)
interquartile range
difference between the values corresponding to the 25th and 7th percentile
Standardised mortality ratio
observed number of deaths / expected number of deaths
maternal mortality rate
maternal deaths / live births
cause specific mortality rate
number of deaths from a particular disease / total population
- crude birth rate
2. crude mortality
- number of live birth / total population
2. number of live death / total population
attrition bias?
in prospective studies, if loss to follow-up occurs disproportionately between the exposed + unexposed groups –> attrition bias can result if the lost subjects differ in their risk of developing the outcome compared to the remaining sugjects
(IT IS A FORM OF SELECTION BIAS)
attrition bias does not occur when the losses happen randomly between the exposed + unexposed groups
Community level intervention - example
taxes on cigarretes can be implemented at the community level to improve health on the public
attack ratio
the ratio of number of individuals who become ill divided by the number of individuals who are at risk
(used in outbreak investigations)
Length time bias
phenomenon whereby by screening test preferentially detects less aggressive forms of a disease + therefore increases the apparent survival time
effect modification is present when
the effect of the main exposure on the outcome is modified by the presence of another variable –> NOT A BIAS (confused with confounding)
health risk assessments
questionnaires that use demographic, medical, lifestyle, and family history information to calculate a patient’s “risk age”
attributable risk vs attributable risk percent
- attributable risk = difference in risk between exposed + unexposed
- attributable risk percent = contribution of a given exposure to the incidence = attributable risk / incidence in exposed
- population attributable risk percent: diseased people due to exposure / diseased people = (incidence of disease in population- incidence in nonexposed) / incidence of disease in population
Maternal death is the
death of a woman while pregnant or within 42 days of termination of pregnancy, irrespective of the duration and site of the pregnancy, from any cause related to or aggravated by the pregnancy or its management but not from accidental or incidental causes.
Allocation bias
the treatment + control groups are assembled. It may occur if subjects are assigned to the study groups of a clinical trial in a non-random fashion. (eg. in a study compating oral NSAID and intraarticular corticosteroids injections for the treatment of osteoarthritis, obese patients may by preferentially assigned to the corticosteroid groups)
Referral bias?
aka: admission rate bias –> the case + control populations differ due to admission or referral practises. (eg. a study involving cancer risk factors performed at a hospital specializing in cancer research my enroll cases referred from all over the nation. However hospitilized control subjects without cancer may come from only the local area)
intention to treat
the patient’s treatment status at the point of randomization is analyzed –> if a patient in placebo begin taking the medication assigned to the treatment group sometime after study initiation, or if a patient in the treatment group stops taking the prescribed medication, the data from these patines is still analyzed along with their original group –> preserves the benefits of randomization and prevents selective bias
nested case control study
design start with cohort studies in which participants are followed over time, and those participants who develop an outcome of interest become cases for a case-control study
positive and negative likelihood ratios indicate
LR+ = sens / (1 - spec) --> probability of an individual with the condition having a positive test / probability of an individual without the condition having a positive test LR- = (1-sensit) / specif) --> probability of an individual with the condition having a negative test / probability of an individual without the condition having a negative test
children - use of prepositions - age
4
changes in elderly - sleep patern
- decreased REM + slow wave sleep
- increased sleep onset latency
- increased early awaking
Hospice model - everything
- Focus on quality of life, not cure or life prolongation
- Symptom control
- Interdisciplinary team (medical, psycosocial etc)
- Services provided at home, assisted living facility or dedicated facility
- REQUIRES SURVIVAL PROGNOSIS LESS THAN 6 MONTHS
Covered by Medicare PART A
