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