RESS Flashcards
The only times you would NOT reference are:
- It is considered common knowledge2. It is your OWN opinion3. It is your OWN data/research
When referencing, how many authors should be listed before ‘et al’ is used ?
6/7
What is a stratified sample ?
Members chosen at random, but sample set into groups (strata) to ensure groups within population are equally represented, based on number of the population that makes up the sample
When is quota sampling useful ?
When time is limited, budget tight or detail not important(As can use opportunistic sample I.e. People who look most helpful in the street)
What is quota sampling ?
Sample taken from stratified population until a pre assigned quota in each stratum is represented.E.g, age rangeTherefore not random!!
Main disadvantage of interval sampling ?
Interval errors can be missed or an unusually high error rate can be detected, depending where you are sampling from
What us cluster sampling ?
Used when ‘natural’ but relatively homogenous groupings are evident in population (e.g. Regions of the UK). Simple random sampling is used within each cluster
Explain categorical data
Can be nominal or ordinal.Categorical variables can only be assigned to distinct categories and do not have a numerical value associated with them
How could ordinal data be made numerical ?
Assigning a rank scale value to each categoryNOTE: the data will still technically be classed as categorical
What is the difference between nominal and ordinal variables ?
Nominal = have NO natural order e.g. SexOrdinal= HAVE natural order e.g. Poor, good, excellentpain has natural order in symptoms (absent, mild, severe) or the Likert scale (strongly disagree, disagree…strongly agree)
What type of data would the number of cases of MRSA on a particular ward be classed as ?
Numerical discrete
What type of data is age classed as?
Numerical continuousNOTE: continuous can be grouped as discrete I.e. Age is often grouped into years- rarely used days, hours, seconds etc
What is relative frequency ?
The percentage of the total frequency accounted for by particular variables
What does a low standard deviation indicate?
That the data points lie close to the mean
How is incidence rate calculated ?
Number of new cases occurring in set period/no. Of people at risk in set period (& time exposed)
What is included in the epidemiological triad ?
Time-person-place
Will Diseases with short duration have high or low prevalence and incidence rates ?
High incidenceLow prevalence
How is mortality rate calculated ?
No. Of people who die from disease in period / no. Of people who die in period (of all causes)
How is data adjusted e.g. For age, gender etc
Stratum specific rates - population split into stratum (age,gender), incidence calculated in each, weighting then assigned to each group & data adjusted accordingly
How is case fatality calculated ?
No. Of people who die for a disease In period / no. Of people with the disease
How are odds ratios calculated ?
Odds for disease of exposed group/ odds of disease of unexposed group
What does a risk ratio (RR) of
Protective effect
When can odds ratios be used in randomised control trials ?
When the RCT is dichotomous
Define dichotomous variables
The variable takes 1 of 2 forms (that are co merely different) e.g. Dead or alive
Type of data histograms can be used for ?
Numerical continuous
What is the use of inter quartile ranges ?
Able to form a graphical representation of probability distribution (box plot)
In normally distributed data what measure would you use to look at spread of data ?
Mean and standard deviation
What measure of distribution should be used in non normally distributed data ?
Median and IQR(So isn’t affected by outliers)Distribution assessed by histogram
What do 95% confidence intervals mean ?
If the experiment were repeated 100 times the results would fall into that range 95 times
What is standard error a measure of ?
How reliable the sample population mean is from that of the population, so measures precision
The CI should not cross the value where the variable is said to have no effect. Where are the points of no impact in ratio and difference ?
Ratio = 1Difference = 0
When is correlation the appropriate statistical analysis
When both the outcome and exposure are numerical
If the outcome is numerical, and the exposure is categorical (independent groups) what is the appropriate statistical analysis ?
T test or Mann-Whitney test
If the outcome is numerical, and the exposure is categorical (non-independent groups) what is the appropriate statistical analysis ?
PAIRED t testSign test
A hypothesis proposed after analysis is which type of hypothesis ?
Inductive hypothesis - explanation as why two sets of info are related to one another
What is a deductive hypothesis ?
A hypothesis proposed before analysis - predict what the relationship will be. You think that at least 2 variables are related to each other
If data is positively skewed, which way will its ‘tail’ be on a box plot ?
Tail to the rightI.e. Q1-Q2
When refining a search, what function does adding an asterisk (*) to the end of a word have ?
Denotes a truncated ending where alternative endings would be acceptedE.g. Teen* would show up teenage, teenagers, teenager, teens
What are Boolean operators ? Give examples.
Words used to refine searches, e.g. AND, OR, NOT
Name two methods that are used to minimise extraneous variables when randomised not possible
Matched-pair analysis (subjects paired with factor of interest e.g. Sex, age etc)Cross over method - subjects are their own control e.g. Take drug for a period and take placebo for a period
What type of study is a census ?
Cross sectional As looks at entire population at defined time assessing prevalence
What is Ansecomb’s quartet ? Relevance ?
4 sets of data with same statistical properties which look very different when displayed graphically - shows importance of graphical representation
What is responsiveness ?
Whether a measure can detect real change (over time?)
What is regression analysis ?
Statistical process for estimating the relationships among variables
What is a type 1 error ?
The incorrect rejection of a true NULL hypothesis- false positive for alternative hypothesis(too optimistic)
What is a type 2 error ?
Failure to reject a false NULL hypothesis- false negative for alternative hypothesis(Too pessimistic)
95% of data lie within how many standard deviations of the mean ?
1.96
What is chi squared used for ?
Determine association between categorical variables
How is standard error calculated ?
Standard deviation/square root of sample size
What is Gaussian distribution ?
Normal distribution
What is Student’s t-distribution ?
A continuous probability distribution that is a little ‘fatter’ than the normal distribution.Used to calculate CIs and in hypothesis testing when the standard deviation of the population is estimated rather than known
What happens after you propose a hypothesis?
Test it - then reject and modify or not reject.
Define population
Every member of a defined group of interest
What is the only true random sample?
Simple random sample - population members are chosen purely a random
What is interval sampling?
When you take samples at set intervals e.g drugs company take a sample of every 100th drug produced to check that it’s being made correctly.
What type of variable is the number of a beds on a ward?
Numerical discrete
What type of variable is weight or height?
Numerical continuous
For what type of data would you use a bar chart?
Categorical and discrete metric variables
For what type of data would you use a pie chart?
Categorical, may be used for numerical data
What is cumulative frequency?
The running total
How do you calculate frequency density?
Freq density = frequency / class width
3 examples of measures of spread?
Range, Standard deviation & IQR
3 examples of measures of central tendency?
Mean, median & mode
Negative skew would result in the greatest spread in what quartile on a box plot?
Lower quartile
Which type of skew would give these results; Q1-Q2 > Q2-Q3?
Negative skew
Give two examples of wildcards used in literature search?
? = one character or none# = only one character but any character
How would you search for eating (related) disorder?
Eating adj1 disorder = searches for eating disorder separated by only one word
What phase of a clinical trial assesses effectiveness and dosage of drugs on a few hundred patients WITH the disease?
Phase II
Two types of reviews?
Systematic - mini reports that are peer reviewed. Focus on specific topic.Non systematic - provide reviews on general topics
What is an erratum?
List of corrected errors, e.g. between editions
What is a consensus study?
A consensus statement developed by professionals via a group consensus process that is intended to advance health professional and/or public understanding of a targeted health problem.
In what type of paper/article/study would you write a short paper discussing any of these 4 things; updating readers on new methods, providing an overview of the topics in an issue, press opposing opinions or clarifying positions?
Editorial
What is an integrated analysis of data from several studies?
Metanalysis
How do you calculate prevalence?
= Number of people with a disease at a certain time / number of people in the population that time
Is prevalence data more valuable in acute or chronic disease? why?
Chronic diseases as it is necessary for the planning and delivery of health services
What is prevalence made up from? (combination)
Incidence (+), recovery (-) & death (- & - population)
How to calculate risk?
Risk = number of new cases / number at risk
In what type of study do you use a risk ratio?
Cohort - used to find risk factors (exposures) disease
In what type of study would you use odds ratio?
Case-control study or RCT
What is relative risk reduction?
RRR = 100 - RR. Essentially its the difference the new treatment makes to the condition (compared to old/untreated group)
Range of values of Risk?
0 to 1
Range of values of Risk ration?
RR 1
Calculate odds of an event?
odds = probability of an event (disease) / probability of the event NOT occurring
Calculate Odds ratio?
OR = odds of disease for exposed group / odds for disease in unexposed group.= probability of disease occurring in exposed group / probability of disease NOT occurring in unexposed group
Which correlation coefficient is used for normally distributed data?
A Pearson correlation coefficient
What correlation coefficient is used when the data is not normally distributed, when one or both of the variables are ordinal, or when the sample size is small?
Spearman’s correlation coefficient
Do larger or smaller studies have a larger CI?
Smaller studies = large CI. Large studies = small CI (larger studies reduce spread of data and inc the accuracy of the result in relation to population)
What do p-values mean?
P = probability of obtaining the results of the test given that the null hypothesis is true
What does p
That there is less than 5% chance that we got the result we did by chance.
Which type of health prevention is this; prevention of disease by treating clinical cases, reducing disability and maximising function?
Tertiary prevention
What term describes this sentence ‘using BMI rather than weight as a measure of obesity’
Validity = measures accurately what it is meant to measure
Definition of reliability
Gives the same result on retesting
What term described this definition ‘can detect real changes when they occur’?
Responsiveness
If T statistic in T test is more than critical value = reject or accept the null hypothesis?
Reject the null hypothesis
‘r’ is what coefficient?
Pearson correlation coefficient. Values lie between -1 & 1
r = -1 then what is the correlation?
Perfect negative correlation
Which Boolean operator would you use to search for synonyms?
or e.g anorexia OR eating disorder
What is opportunity cost?
Choosing A over B means giving up B which implies the value of the benefits from A is greater than from B.Opportunity cost is the value of forgone benefit which could be obtained from a resource in its next best alternative use
Disease incidence & mortality are what types of health outcomes? Record based, biological and clinical outcomes or clinical and patient reported outcomes?
Record based
Give examples of biological or clinical based health outcomes?
Lab results, BMI, bp. body temp
Global ratings, symptom score and QoL are examples of what type of health outcome?
Clinical and patient recorded outcomes
What does PROMs stand for?
Patient reported outcome measures - measure quality from the patient perspective
What three key things should health outcomes be?
1) Valid2) reliable3) responsive
Benefits of knowing health outcomes?
- identify treats and procedures that work and which are less effective- identify national and international variation- monitor performance against targets and over time
What is the purpose of the medical record, list 6 things…
Teaching, National statistics, commissioning, Audit, legal, research and evidence.
Type of efficacy described as ‘obtaining maximum output from a set of given resources’?
Technical efficacy - is concerned with how best to deliver a programme, or achieve a given objective
Type of efficacy described as ‘production that matches the consumer demand’?
Allocative efficacy
Term used to described this statement ‘concerned with the fairness or justice of the distributions of costs and benefits.’
Equity - another criterion for allocating resources, who benefits may matter to society.
Difference between efficiency and equity w.r.t health economics?
Efficiency looks at the total benefit without considering who actually benefits whereas equity looks at the distributions of costs and benefits and whether it is fair and justifiable.
What type of efficacy does cost effectiveness analysis address?
Technical efficiency
Does cost utility analysis address allocative or technical efficiency within the health care budget?
Allocative
What is the threshold for cost-effectiveness also known as?
Willingness to pay threshold
What is the NICE threshold for maximum willingness to pay for health gain?
£20,000 - £30,000
Does all health expenditure have an opportunity cost?
YES
When do you not need ethical approval?
Audits/evaluations
