4. Sources of Variation Flashcards
Define prevalence.
The number of cases at a particular moment in time.
Define incidence rate ratio.
The relative difference of incidence rates in groups.
Define observed values in relation to true tendency.
The observed value is the best estimate of the true or underlying tendency.
Define hypothesis.
A statement where an underlying tendency of scientific interest takes a particular quantitative value.
What can be said if p-value
The data is inconsistent with the he stated hypothesis so there is enough evidence to reject the hypothesis. The data is statistically significant.
What are three limitations of hypothesis testing?
The p-value
Define incidence.
The occurrence or frequency of a disease.
What is the 95% confidence interval?
The range within which we can be 95% confident that the true value really lies.
What could be concluded about a confidence interval of 0.59 - 1.14? (Null hypothesis = 1).
The null hypothesis is consistent with the data so cannot be rejected, p>0.05.
How do you work out the 95% confidence limits?
Lower 95% confidence limit = observed value / error factor
Upper 95% confidence limit = observed value x error factor
95% confidence limit range: lower limit to upper limit.
What is the formula for error factor?
Error factor = exp. (2 x squared root (1/cases)).
What happens to the error factor and confidence intervals when more data is collected?
The error factor gets smaller and the confidence interval get narrower.
