The first few lines of code should assign values to the parameters needed and the script prints only the PPV (and nothing else).

You are asked by a medical doctor to write a simple Matlab script that computes the positive predictive value of a medical test (does not matter what test for this exercise). No medical test is perfectly accurate and we have various numbers (statistical measures) to describe how accurate they are. The two most popular are sensitivity and specificity. According to wikipedia, Sensitivity measures the proportion of positives that are correctly identified (i.e. the proportion of those who have some condition (affected) who are correctly identified as having the condition) and Specificity measures the proportion of negatives that are correctly identified (i.e. the proportion of those who do not have the condition (unaffected) who are correctly identified as not having the condition). If you are not sure what these mean, do not worry. They are just numbers between zero and one. We also need the prevalence that is the proportion of the people that have the disease we are testing for. The positive predictive value of a medical test is the ratio of the number of true positives, versus the number of all positives (true and false). In simpler terms, what is the probability to have the disease if you test positive. Again according to wikipedia the formula we have to use is: sensitivity