eM3 – Displaying data Flashcards
X = Categorical Y = Counted quantitative
Pie chart
X = Categorical/counted quantitative Y = Quantitative
Bar chart
X = Continuous quantitative Y = Quantitative counted
Histogram
X = Categorical Y = Continuous quantitative
Dot plot / Box and whisker
X = Continuous quantitative Y = Continous quantitative
Scatter plot
When would you use a pie chart?
X = Categorical Y = Counted quantitative
When would you use a bar chart?
X = Categorical/counted quantitative Y = Quantitative
When would you use a histogram?
X = Continuous quantitative Y = Quantitative counted
When would you use a dot plot?
X = Categorical Y = Continuous quantitative
Difference to the bar chart because shows the distribution of data best for small amount of data
When would you use a box and whisker diagram?
X = Categorical Y = Continuous quantitative
When would you use a scatter plot?
X = Continuous quantitative Y = Continous quantitative
show similarities
What does box and scatter plot represent and show?
- lower extreme
- lower quartile
- median
- upper quartile
- upper extreme
interquartile range
whisquers show= extremities
But they are used more for non parametric data
What are the line graphs used for?
Line graph: a diagram showing a line that joins several points and more often used to show the impact of time on a dependent variable. An advanced form of a line graph is a Kaplan-Mieir graph that is used for survival analysis.
What are the Cumulative frequency curve used for?
Cumulative frequency curve: This is similar to a frequency histogram but uses a curve rather than bars and accumulates the numbers as we proceed along the x-axis. A variation on the cumulative frequency curve is a dose-response curve used in pharmacology, which you will have encountered.
What are the Bubble plots used for?
Bubble plots: This is similar to a scatter plot, but the size of the bubble can represent a third variable. They are good for information visualisation but not always considered scientifically accurate.
What are the Stem & leaf plot used for?
Stem & leaf plot: these are similar to a frequency histogram or a dot-plot and display the general distribution of the data. They can be considered as a ‘hybrid’, somewhere between a table and a graph. However, they are only useful for moderately sized data-sets.
List 6 types of studies in order of evidence from strongest to weakest
- Systematic reviews & meta-analyses
- Randomised control trails
- Well-designed control trials (non-randomised)
- Case-control studies
- Systematic review of descriptive studies
- Descriptive cross-sectional studies
7, Case report/series
What are levels of evidence?
Evidence is classified according to strength.
- strongest evidence is from analysis of large data sets (e.g. meta-analyses, systematic reviews and randomised controlled trials). Only evidence of this nature can yield strong recommendations.
Non-randomised observational studies such as case-control studies can yield only weak recommendations.
What is the risk reduction?
1 - RR
What is meant by a 95% confidence intervall?
A 95% confidence interval is a range of values that you can be 95% certain contains the true mean of the population
What is relative risk?
The ratio of the probability of an event occurring in the treatment group to the probability of the event occurring in the comparison, placebo group.
RR<1 = lower probability in treatment group e.g. RR of 0.5 indicates risk is halved
RR=1 same probability
RR>1 higher probability in placebo group
Define Primary Outcome measure
the outcome that a researcher considers to be the most important among the different outcomes that are to be examined in the study.
Define Randomised Controlled Trials
A study in which people are allocated at random (by chance alone) to receive one of several clinical interventions. One of these interventions is the standard of comparison or control. The control may be a standard practice, a placebo (“sugar pill”), or no intervention at all.
Define Systematic Reviews
A systematic review summarises the results of available carefully designed healthcare studies (controlled trials) and provides a high level of evidence on the effectiveness of healthcare interventions.
Define Meta-analyses
A quantitative, formal, epidemiological study design used to systematically assess the results of previous research to derive conclusions about that body of research.
Define Case control studies
A study that:
- compares patients who have a disease or outcome of interest (cases) with patients who do not have the disease or outcome (controls),
- and looks back retrospectively to compare how frequently the exposure to a risk factor is present in each group
- to determine the relationship between the risk factor and the disease.
Case control studies are observational because no intervention is attempted and no attempt is made to alter the course of the disease.
Define Relative risk
The ratio of the probability of an event occurring (i.e. skeletal fracture) in the treatment group to the probability of the event occurring in the comparison, placebo group.
Define Odds ratio
A measure of association between an exposure and an outcome or the odds of an outcome in the treatment group divided by odds of an outcome in the control group.
If the outcome is negative, an effective treatment will have an odds ratio <1;
If the outcome is positive, an effective treatment will have an odds ratio >1.
What does it mean when X^2 is 0?
The observed and expected frequencies are the same
The higher the X^2 value…
the bigger the difference between the observed and expected frequencies.
