Year 2 Brainscape Qs Flashcards
What is the formula for standard deviation? [1]
Square root of an average of all the individual points’ (distances from the mean)2
What measures of location and spread are used in a data contained in normal distribution? [2]
Mean and standard deviation
What measures of location and spread are used in the presence of outliers in the data? [2]
Median and interquartile range [2]
What change in standard deviation flattens the curve and what makes it taller and thinner? [2]
Flat: Increased SD
Tall and thin: Decreased SD
How many standard deviations from the mean
(+ and -) is 90%, 95% and 99% of population contained? [3]
90%:1.64 SD
95%: 1.96 SD
99%: 2.58 SD
How is standard error calculated and when is it used? [2]
SE = Standard deviation / sq root (sample size)
It is used as a standard deviation of the distribution of all possible sample means (used when dealing with sampling from the population)
How is confidence interval calculated? What does 95% CI = 21.4 to 22.6 mean BMI? [2]
95% CI = sample mean =/- 1.96 x standard error
It means that we are 95% sure that in the population the mean BMI can be as low as 21.4 and as high as 22.6.
What happens to CI if the sample size is increased? [1]
The confidence interval gets narrower
Which variable in the linear regression equation indicates outcome and which is the predictor? [2]
Y – outcome
X – predictor
What test is used to establish p-value while comparing two means? [1]
Two sample t-test
What are different types of clinical trials? [3]
Uncontrolled – everyone gets treatment
Controlled – treated group (‘new treatment’) vs untreated group (placebo or ‘standard treatment’)
Randomized controlled – allocation to groups is determined by chance
What are the types of blinding? [2]
Single blind: patients don’t know what treatment they’re getting
Double blind: both patients and observers (examining doctors) don’t know what treatment each patient is getting
What type of randomized controlled trail is used if the treatment is irreversible and which if it’s reversible? [2]
Irreversible: parallel group
Reversible: crossover
Name two disadvantages of crossover design? [2]
How can we compensate for one of them? [1]
Time consuming
Carry-over effects: washout period before second treatment
What is the difference between intention-to-treat and on-treatment analyses? [2]
Which one is better and why? [2]
TT: compare all subjects in treatment group regardless of whether they complied and acc took the drug
OT: compare subjects who acc took the treatment
ITT is better as it is a better representation of what would happen in real life
When is relative risk statistically significant? [1]
When 95% CI for that relative risk excludes 1
What would be the relative risk if the treatment didn’t have any effect?
RR = 1
What is the type of diagram used in meta-analyses? [1]
Forest plot
What diagram is used to assess publication bias of meta-analyses?
Funnel plot
Give overview of a design of cohort studies? [3]
What is the main question of cohort studies? [1]
Identify cohort
Measure exposure
Follow up over time to identify whether they have disease or not
Is the disease more common in exposed or unexposed?
What are the sources of bias in the cohort studies? [2]
Loss (of people) to follow-up
Measurement of exposure at only one point in time (it can change very rapidly); selection of cohort
How is relative risk measured in cohort studies? [1]
Incident of disease in exposed population / incidence of disease in unexposed population
What curve is used in survival analyses? [1]
What information does it provide? [1]
Kaplan-Meier curve; shows the proportion of people surviving over time
What is a hazard ratio? [1]
Risk of dying at any time point in one group compared to the other
How can the absolute excess risk be calculated? [1]
Risk in exposed – risk in unexposed
How is attributable proportion calculated? [1]
P(RR-1) / 1+p(RR-1) ; p= proportion exposed in population
What is the design of case-control studies? [3]
Identify those with disease [cases]
Measure exposure (from the past)
Identify those without disease [controls] and measure exposure (from the past)
What study design is useful for biomarkers studies where biomarkers are v expensive to measure? [1]
Nested case-control studies
What is the design of a nested case-control study design? [4]
Identify cohort and take & store blood sample
Follow up over time and detect if have disease.
All people with disease are cases and those without disease are selected for controls.
Measure exposure in cases and controls from the biomarkers.
What does odds ratio represent in rare disease? How do you calculate it? [1]
Relative risk; odds exposure in cases/odds exposure in control
How do you calculate absolute excess risk? [1]
(Odds ratio x risk of disease) – risk of disease
What does cross-sectional study measure? [1]
Measure existing disease and current exposure
Which study design has the biggest risk of bias? [1]
Cross-sectional surveys [1]
What study design has the bigger risk of confounding: cohort or case-control? [1]
Case-control studies
What study design would you use for rare disease? [1]
What study design would you use for rare exposure? [1]
Rare disease: case-control study
Rare exposure: cohort study
State the definition of incidence [1] and prevalence [1]
Incidence: Number of new cases of the disease occurring within a period of time
Prevalence: Number of cases of the disease that are present in a particular population during a period of time/particular date
What is the Declaration of Helsinki?
Ethical principles for medical research involving human subjects – promotes and safeguard health, wellbeing and rights of research. It’s the duty of physicians who are involved in medical research to protect life, health, dignity, integrity, right to self-determination, privacy and confidentiality of personal info of research subjects
List 5 types of cognitive bias [5]
Availability (disease seen most recently = most likely)
Representativeness (diagnosis more likely if more similar to typical cases)
Anchoring (perceived probability of diagnosis based on one trait);
Diagnosis momentum (once labelled it’s hard to go back); Fundamental attribution error (tendency to blame ppl for their illness and sometime; commission bias (action rather than inaction)
The reference range for 90% STD is
mean ± 1.69 SDs
mean ± 1.96 SDs
mean ± 1.64 SDs
mean ± 1.94 SDs
mean ± 2.58 SDs
The reference range for 90% STD is
mean ± 1.69 SDs
mean ± 1.96 SDs
mean ± 1.64 SDs
mean ± 1.94 SDs
mean ± 2.58 SDs
The reference range for 99% STD is
mean ± 1.69 SDs
mean ± 1.96 SDs
mean ± 1.64 SDs
mean ± 1.94 SDs
mean ± 2.58 SDs
The reference range for 90% STD is
mean ± 1.69 SDs
mean ± 1.96 SDs
mean ± 1.64 SDs
mean ± 1.94 SDs
mean ± 2.58 SDs
What value is changing between the different colours in this Gaussain Distribution?
Standard error
Standard deviation
Mean
Median
Inter quartile range
STD
What value is changing between the different colours in this Gaussain Distribution?
Standard error
Standard deviation
Mean
Median
Inter quartile range
What does 95% STD actually mean? [1]
95% of all values are within 1.96 standard deviations of a mean value
What does 95% STD actually mean? [1]
95% of all values are within 1.96 standard deviations of a mean value
Which regression model would you use for the following?
Exponential growth
Exponential decay
Sigmoid
Polynomial – quadratic
Exponential growth
Which regression model would you use for the following?
Exponential growth
Exponential decay
Sigmoid
Polynomial – quadratic
Polynomial – quadratic
Label A-C
A: parralel
B: cross over
C: factorial
Place the following in order of most to least likely to have bias
Case-control
Cohort
Clinical trial
Cross-sectional survey
What do A & B represent on this forest plot? [2]
A: Result of study
B: 95% CI of result
What does the diamond represent on the forest plot? [1]
The diamond represents the point estimate and confidence intervals when you combine and average all the individual studies together.
Describe the differences in horizontal and box size in forest plots in samll versus big studies [2]
The bigger the study, the smaller the horizontal line and bigger the black box representing the point estimate.
The smaller the study, the wider the horizontal line and smaller the black box representing the point estimate.
The forest plot shows the results of randomised trials of aspirin versus placebo in the prevention of preeclampsia.
Which was the biggest trial?
Ebrashy: has the biggest box
.Measures of inequality are important to track patterns and trends in ill-health in order to prioritise service provision.
Please show your understanding of these issues by labelling the following graph.
Use the following labels:
Healthy life expectnacy, multi morbidities percentile, race, gender, healthcare access, neighbourhood deprivation percentiges
Label A&C of this funnel plot [2]
A: 95% CI
B: Study precision
C: Overall effect
D: Study result
Describe the results of this funnel plot [1]
Asymmetrical: indicates bias
What study types is this graph often used in?
A. Cohort study
B. Case control study
C. Clinical trial
D. Cross-sectional survey
A. Cohort study
B. Case control study
C. Clinical trial
D. Cross-sectional survey
Kaplan-Meier curves
Plot proportion of people surviving over time
Compared using a log rank test
Used in cohort studies and randomized trials.
This trial demonstrates a
case-control study
cohort study
factorial study
cross sectional study
case-control study
This trial demonstrates a
case-control study
cohort study
factorial study
cross sectional study
cohort study
