Important statisitcs Flashcards
What is risk? - What is the risk of disease in smokers if 20 smokers in a group of 100 develop the disease?
Risk is a percentage. 20/100= 20% of smokers
What is risk ratio?
Risk ratio is when you compare the risks of two groups
What is relative risk reduction?
Comparing the adverse events in an exposed group vs an unexposed group.
What is experimental event rate?
Risk of adverse events in the exposed group.
What is control event rate?
Risk of adverse events in control group.
How to calculate relative risk reduction? EER is 94 and CER is 82
Experimental event rate- control event rate/ control event rate. Relative risk reduction would be 0.15.
What does relative risk reduction indicate?
How much the treatment reduced the risks of an adverse event in exposed group controlled to unexposed group
What is the issue with calclating cumulative risk?
It does not takie into account that some people may leave a study or enter it at diferent times due to migration or death so there may be attrition bias. Therefore, incidence rate is used, as it uses person-years which is the sum of each particpant’s entery into the study-> developing disease. Incidence rate is a true rate
How is odds value expressed?
As a raw value. Odds cannot be put as a percentage.
What is standard deviation?
The range of values around the mean.
What is z value?
How many standard deviations a value is from the mean.
What is low standard deviation?
Higher accuracy; lower range of values around the mean.
What is high standard deviation?
Lower accuracy; greater range of values around the mean.
What is tail of distribution?
Extreme regions of distribution in a skewed graph. The area the tail is in indidcates a positive/right skew or negative/left skew.
What is standard error?
Approximate standard deviation of a statistical sample population. Measures the variability across different samples in a population.
What is reference range?
A range of values that is deemed normal for a physiological measurement in healthy people.
What is confidence interval?
Range of values where the true value lie, generally + or - 1.95
What is the meaning of a unimodal graph?
Singular peak
What is the meaning of a bimodal graph?
Two peaks
What are the features of a positive skew?
Mean and median is greater and to the right, mode stays the same. Median is between the mode and mean.
What are the features of negative skew graph?
Mean and median is lower and to the left, mode is the same. Median lies between the mode and mean.
What is cumulative incidence?
Incidence rate in a given time period, such as 5 years. Only consider the incidence on year 1 and year 5 for comparison. Incidence/time period.
What is absolute risk?
Probability of an event, including both the exposed and the control group.
How to calculate absolute risk? Exposed group has 1000 people and 50 people with disease. Control group has 700 people and 56 people with disease.
Incidence in Exposed risk +control/ total number in both group. 50+ 56/1000 + 700=0.062 or 6.2% absolute risk.
What is meta analysis?
Comparing multiple similar studies with a statistical method.
What is systematic review?
Using rigorous and transparent method to synthesise the data of multiple relevant studies in a single document.
What is Phase 1 drug trial?
Measure tolerance in healthy participants
What is Phase 2 drug trial?
Measure efficacy in healthy and diseased participants
What is Phase 3 drug trial?
Measure efficacy of drug compared to alternative drug
What is Phase 4 drug trial?
Measure the long term side effects of a drug
What is a one tailed graph?
Alternative Hypothesis which specifies a postivie or negative effect and goes in one directiion
What is a two tailed graph?
Alternative hypothesis which does not specify a postivie or negative effect and goes in both directions
What is p value?
Probability of an outcome occuring if the null hypothesis is true
What does a small p value indicate?
Reject null hypothesis- Likely the outcome will occur
What does a large p value indicate?
Do not reject null hypothesis- likely null hypothesis is true
What is a competing hypothesis?
Alternative hypothesis that goes against another alternative hypothesis
What are the databases we use for systematic review?
Pubmed, Cochrane library, Google Scholar, NICE, Embase
What is a orest plot?
Forest plots summarise findings from multiple papers by identifying a common statisitc. It is useful for systematic review and meta analysis,
What does the diamond represent in fox plots?
Summary of all the data points. Centre is the overall effect estimate and width is the confidence interval
What is the value of the vertical line in fox plots?
Null effect, which is equal to 1. The closer it is to the null effect, the less significant it is.
What is the black box represent in fox plots?
Study/point of estimate.
What does the line represent in fox plots?
95% confidence interval.
What is absolute risk reduction?
Difference in risk between the placebo and treatment group
What is correlational studies?
Observational studies to examine event exposure, disease prevalence and risk factors
