Lecture 4; Introduction To Epidemiological Investigations Flashcards
What is epidemiology?
The study of distribution and determinants of health-related states or events (including disease) and the application of this study to the control of diseases and other health problems
What are the various methods used to carry out epidermiological investigations? (2)
- surveillance and descriptive studies can be used to study distribution
- analytical studies are used to study determinants.
What is the difference between statistics and probability?
Statistics; given the information you have, what can you infer about the population
Probability; given the population what can you infer about a small group
Why is a sample drawn?
To enable inference about the population
What should a sample for a study be?
-as representative as possible
Remember that all samples drawn from the same population vary
What is prevalence?
Prevalence=incidence x duration of disease
It is a proportion not a rate (like taking a slice of cake)
(You cannot get over 100% prevalence because it is a proportion, there are no units- it counts people- people divided by people, the denominator is persons not persons per time because we look at point prevalence, study is a cross-sectional survey ie there is no follow up)
What is incident rate? How do you calculate it?
-measuring new cases
(Counts cases not people, need to know time-period at risk-and cases and people)
Incidence rate= New events/ (person x time in years)=events per person per time (yr)
Ie 300/50,000x1.5=0.004 heart attacks per worker per year
Therefore 4 heart attacks per 1,000 workers per year
What does p-y mean?
Person years
What happens to prevalence if you: A)increase incidence B)cure more patients C)kill more patients D)keep them alive longer
A) increase prevalence
b) lower prevalence
C) lower prevalence
D) increase prevalence
Remember that what you see (observation) is not always what you expect (the tendency)
.
What is our observed value?
Our best estimate of the true or underlying tendency
What is a hypothesis?
A statement that an underlying tendency of scientific interest that takes a particular quantitative value
What is the p-value?
When you perform a hypothesis test in statistics, a p-value helps you determine the significance of your results. … The p-value is a number between 0 and 1 and interpreted in the following way: A small p-value (typically ≤ 0.05) indicates strong evidence against the null hypothesis, so you reject the null hypothesis.
If the p value is greater than or equal to 0.5 what does this mean?
We have not rejected the null hypothesis
***Does not mean the hypothesis has been proven
When might p value not work?
If your sample size is too small (ie 3 coin tosses)
