A set of training materials for professionals working in intervention epidemiology, public health microbiology and infection control and hospital hygiene.
Need help with your investigation or report writing? Ask the Expert. Free advice from the professional community.
You can't make decissions on this page's approval status because you have not the owner or an admin on this page's Group.
Mathematical models can be as simple as a straight line. In a linear model the straight line is used to describe the relation between two variables. We express y according to the value of x. We predict y according to x. Therefore x is called the predictor or independent variable and y the predicted or dependent variable.
Figure 1 shows the relation between y and x.
The straight line represents the average values of y for different values of x. It is a regression line. It was obtained by fitting a straight line equation to the data. A simple way to understand how the straight line is fitted on the dot plot is to visually guess where it would need to be placed in order to minimise the various distances between each dot and the line.
The equation of a straight line is:
y = β0 + β1x
β0 is the intercept (value of y when x = 0)
β1x is the coefficient of x. It describes the slope of the line. It represents the number of units of change in y when x increases by 1 unit.
Let's suppose that in the above example we want to predict y not only according to x1 but also according to x2. We would have then two predictors. The relation between x1 , x2 and y is still a straight line. The equation is now:
y = β0 + β1x1 + β2x2
To locate the straight line in the dots we need to imagine a 3 dimensional rectangle coordinates with y expressed according to x1 and x2.
The coefficients β1 and β2 respectively provide estimate of the effect of x1 and x2 which are mutually un-confounded. Mathematically there are no limits to the number of variables to be included in a model.
<<Back to Logistic regression
Join the discussion about this article in the forum!
rfilipe posted on 11/6/2015 2:38:36 PM:
I've been trying to learn more about how the steps for outbreak investigations and found other sources which present a list of steps for outbreak investigations.
I understand that different contexts require different adaptations of the steps and can only guess that there are more variations. I would like to leave here the challenge to compare the different approaches and enrich the FEM Wiki articles with this analysis. Is there anyone who has already invested some work on this? As an inspiration, a friend pointed me out to the Wikipedia article on the 10 commandments, which in fact are 14 and each religion talks about the 10 commandments referring to a selected subset of those 14.
You need to be logged in to post comments.
You can log in here. You can register here if you haven't done so yet.