Research methods/ stats/ethics/Canmeds Flashcards
What is specificity
The ability to confirm absence of the disease
true negative rate
Positive predictive valve
the probability of disease if the test is positive
Negative predictive value
Is the probability of absence of disease if the test is negative
What is null hypothesis
defined as lack of difference between the two treatments
What is a type 1 error
rejecting the null hypothesis when it is true
False positive rate
Occurs when a statistically significant difference is found, when really there is no difference
It is based on the choice of the level of statistical significant p < 0.05
What is a type 2 error
not rejecting the null hypothesis when it is false
Chance that the study finds no difference when in fact there is a difference
Chance of a type II error is inversely related to the sample size and to the statistical power
List Bias associated with meta anlalysis studies
What techniques can be done to reduce bias?
What technique to test for Heteogenity
List 2 strengths of Metanlysis
- Publication bias/Search Bias/Selection bias
- “Funnell plot”
- Forest Plot–and a subsequent cochran Q- test
- Strengths:
a. Increased Effective sample size which greatly increases more outcomes and variable that can be examined
b. Allows examining of rare events
What is major strength of RCT compared to Observational study?
List 2 ways that Observational studies attempt to account for weakness
List 3 potential limitations of RCT
RCT eliminates selection bias
Propensity analysis and Risk adjustment techniques (such as regression or analysis of variance)
weakness of RCT
a. decreased generalizability--specific inclusion/exclusions b. Inadequate statistical power --expensive to enroll pts c. Follow-up and approach to treatment may not be representative of real life
What is c statistics
probability that predicting the outcome is better than chance.
Used to compare the “goodness of fit” of logistic regression models, values for this measure range from 0.5 to 1.0.
value of 0.5 indicates that the model is no better than chance at making a prediction of membership in a group and a value of 1.0 indicates that the model perfectly identifies those within a group and those not.
Models considered reasonable when the C-statistic is higher than 0.7 and strong when C exceeds 0.8
What is p value
p-value is the probability of obtaining a test statistic at least as extreme as the one that was actually observed, assuming that the null hypothesis is true. One often “rejects the null hypothesis” when the p-value is less than the predetermined significance level which is often 0.05 or 0.01, indicating that the observed result would be highly unlikely under the null hypothesis. Many common statistical tests, such as chi-squared tests or Student’s t-test, produce test statistics which can be interpreted using p-values.
What is null hypothesis
the null hypothesis refers to a general or default position: that there is no relationship between two measured phenomena,or that a potential medical treatment has no effect.Rejecting or disproving the null hypothesis – and thus concluding that there are grounds for believing that there is a relationship between two phenomena or that a potential treatment has a measurable effect – is a central task in the modern practice of science, and gives a precise sense in which a claim is capable of being proven false.
What is C statistic
A measure that indicates how well a prediction model or risk score discriminates between pts who do and who do not have an event.
e.g., “how well a value (predicted lactate clearance) is able to discriminate between patients who had an event (death, MI, etc)
A C-statistic is good if it’s greater then 0.8 as a good utility, valves from 0.7 to 0.8
A value of 1.0 is assigned to a prediction model or risk score with a perfect ability to discriminate between pts who do and do NOT have an event
What’s type I error an type II error
Itype I error (or error of the first kind) is the incorrect rejection of a true null hypothesis. A type II error (or error of the second kind) is the failure to reject a false null hypothesis. A type I error is a false positive. Usually a type I error leads one to conclude that a thing or relationship exists when really it doesn’t.
A type II error is a false negative.
When comparing two means, concluding the means were different when in reality they were not different would be a Type I error; concluding the means were not different when in reality they were different would be a Type II error.
What is odds ratio
The odds ratio is a measure of effect size, describing the strength of association or non-independence between two binary data values. It is used as a descriptive statistic, and plays an important role in logistic regression. Unlike other measures of association for paired binary data such as the relative risk, the odds ratio treats the two variables being compared symmetrically, and can be estimated using some types of non-random samples.
What is relative risk
In statistics and mathematical epidemiology, relative risk (RR) is the risk of an event (or of developing a disease) relative to exposure. Relative risk is a ratio of the probability of the event occurring in the exposed group versus a non-exposed group
In a simple comparison between an experimental group and a control group:
A relative risk of 1 means there is no difference in risk between the two groups.
An RR of < 1 means the event is less likely to occur in the experimental group than in the control group.
An RR of > 1 means the event is more likely to occur in the experimental group than in the control group.
If a patient is incapable of a decision the order of who is selected is?
What ethical principle justifies not obtaining informed consent
A person specified by the patient when capable A court appointed person A spouse A child A brother relative or friend
Beneficence is the ethical principle
The standards of disclosure in western legal systems
Professional standard: what other physicians tell the patient
Reasonable person standard: what a reasonable person would want to know.
Particular person standard: What a reasonable person in the particular circumstance as the patient would want to know
What is Survival Analysis
involves the modeling of time to event data; in this context, death or failure is considered an “event” in the survival analysis literature – traditionally only a single event occurs for each subject, after which the organism or mechanism is dead or broken.
What is Hazard ratio
In survival analysis, the hazard ratio (HR) is the ratio of the hazard rates corresponding to the conditions described by two levels of an explanatory variable.
Example, in a drug study, the treated population may die at twice the rate per unit time as the control population. The hazard ratio would be 2, indicating higher hazard of death from the treatment. Or in another study, men receiving the same treatment may suffer a certain complication ten times more frequently per unit time than women, giving a hazard ratio of 10
What is major strength of RCT compared to Observational study?
List 2 ways that Observational studies attempt to account for weakness
List 3 potential limitations of RCT
RCT eliminates selection bias
Propensity analysis and Risk adjustment techniques (such as regression or analysis of variance)
weakness of RCT
a. decreased generalizability--specific inclusion/exclusions b. Inadequate statistical power --expensive to enroll pts c. Follow-up and approach to treatment may not be representative of real life
What are key aspects of PROFESSIONAl
Committed to the health and well-being of individuals and society through ethical practice, profession-led regulation, and high personal standards of behaviours
Comitment to clinical competence, the embracing of appropriate attitudes and behaviors, integrity, altriusm, personal well being and to the promotion of the public good within their domain
What is major strength of RCT compared to Observational study?
List 2 ways that Observational studies attempt to account for weakness
List 3 potential limitations of RCT
- Publication bias/Search Bias/Selection bias
- “Funnell plot”
- Forest Plot–and a subsequent cochran Q- test
- Strengths:
a. Increased Effective sample size which greatly increases more outcomes and variable that can be examined
b. Allows examining of rare events
Describe levels of Evidence
level A evidence = data derived from multiple randomized trials or metal-analyses
Level b: data from single randomized trial or non randomized trial
Level c: only consensus opinion from experts
Five Conditions that must be met for ethical research
A: The existence of clinical equipoise
A: Good design
A: Sound foundation of previous work must give good reason to believe that the proposed interventions will achieve the intended result
A: Research interventions are not likely to cause tserious harm to the research subjects
A: Prior approval by a Research Ethics Board
Define clinical equipipose
This exists when the expert medical opinion remains divided over the best choice among treatment options; the medical community is unable to achieve consensus on the preferred treatment
Distinguish euthanasia and assisted suicide from decisions to forego treatment
A: Euthanasia and assisted suicide involve the injection of a lethal substance or the provision of a lethal overdose
A: Decisions to forego treatment involve the non-initiation or discontinuation of a life-sustaining treatment such as CPR, ventilator, tube feeding, etc. The law permits discontinuation, even though it leads to death, under defined conditions
Define competence
A: Possession of the required knowledge, skill, and experience to perform a particular task reliably and produce an appropriate outcome
A: It is a categorical variable; one is competent, or not, to provide a particular service or perform a particular operation
What are the elements of informed consent
Capacity: the patient is able to understand the risks and benefits of treatment vs non-treatment
Voluntariness: The patient is not subjected to coercion
Disclosure: the patient is informed enough to give consent
the right to accept or refuse treatment is preserved by the charter of rights in canada
Q: What are the 3 standards for how the decision should be made, in decreasing order of priority?
A: Wishes – Prior expressions by the patient, while competent that seem to apply to the actual decision that needs to be made
A: Values and beliefs
A: Best interests – This is more important for children, where the decision maker is usually the parent; decisions should be respected unless they would cause direct and serious harm to the child
Q: What are the 3 important aspects to informed consent as per the Royal College?
A: Disclosure – Information about the risks and benefits of the proposed test or treatment as well as any alternatives, presented in language that the patient can understand
A: Capacity – The ability to understand and appreciate the consequences of a particular decision or lack of decision; If in doubt, consultation from a psychiatrist, hospital attorney, or ethicist may be helpful, the ultimate judge of a patient’s capacity is court; If the patient is incapable, seek consent from the appropriate substitute decision maker
A: Voluntariness – The ability to make treatment choices without undue external coercion
What are the 7 CanMEDS
Scholar Manager Health Advocate Collaborator Communicator Professional Medical expert
Q: What are the 7 CanMEDs roles?
A: Medical expert – Diagnostic and Therapeutic skills, effective patient care, access and apply information, consultation
A: Communicator – Therapeutic relationship, relevant history, listen effectively, discuss appropriate information
A: Collaborator – Consult effectively, multidisciplinary team
A: Manager – Utilize and allocate resources, health care organization, use information technology
A: Scholar – CME, facilitate learning, critically appraise the literature, contribute to new knowledge
A: Health advocate – Identify determinants of health, for patients and community, recognize and respond
A: Professional – Integrity, honesty, and compassion, interpersonal behaviours, practice medicine ethically consistent with obligations
