Question: We took a simple random sample of 1000 people, and for each one we checked whether or not he got the flu in 2012 and whether or not he got the flu in 2012. We obtained two responses for each of the 1000 people. To evaluate if there is an association between these two qualitative variables (having flu or not) and (having been vaccinated or not) from the data of our sample: 
 Options:  <1> We draw a quantile-quantile graph. <2> We perform a t test for the difference of means. <3> We calculate the Pearson correlation coefficient. <4> We make a contrast of the signs for the difference of medians. <5> We make a contingency table and an independence test.
5