Incidence and Prevalence Flashcards
What is prevalence?
A measure of how common a disease is.
What 2 ways can prevalence be expressed?
- Percentage
2. Number per n people
What are the 3 types of prevalence?
- Point prevalence
- Period prevalence
- Lifetime prevalence
What is point prevalence?
The proportion of individuals with the condition at a specified point in time.
What is period prevalence?
The proportion of individuals with the condition at any time during a specified time interval.
What is lifetime prevalence?
The proportion of individuals with the condition at any point in their lives.
Prevalence calculations must always be accompanied by a written explanation. How would a point prevalence of 4/200 students with bunions be explained?
The point prevalence of bunions in these students is 2% (or 2 per 100).
What is incidence?
The rate at which new events occur in a population, over a defined period of time.
What 2 ways can incidence be expressed?
- Per n people per time period
2. Per n person-years
What is person-years?
A measurement combining (multiplying) the number of people observed and the number of years they were observed for.
What are 4 factors affecting prevalence? (Epidemiologists bathtub!)
- Death rate
- Recovery rate
- Incidence rate
- Migration rate
In terms of sample data, what is the point estimate?
The point estimate is the best guess based on sample data.
What is the sampling error?
The differences between the sample point estimates and the truth.
What is the standard error?
A numerical value that represents the sampling error.
What is a confidence interval?
The confidence interval (CI) is a range of values that’s likely to include a population value with a certain degree of confidence.
What is the formula for calculating Confidence Intervals?
Lower bound = point estimate - (1.96 x S.E.)
Upper bound = point estimate + (1.96 x S.E.)
