I am a beginner to statistics. I have a data set which includes age, sex, weight, number of sick days for 300 people. I have to take into account confounding variables (age, sex) when I analyse the data. So I have split the data into male and female and for both groups i am now looking at whether there is a correlation between weight and number of sick days taken, but i still need to factor in their ages too (the other confounding variable). how do i do this when analysing data on excel? do i need to further divide the data into subgroups depending on age?
You need to use regression. I am assuming number of sick days is the dependent variable. In this case, you probably need some form of count regression, and likely a zero-inflated form (e.g. zero-inflated Poisson or zero-inflated negative binomial). I don't think these are available in Excel and, in any case, I would not use Excel for statistical analysis.
If you are going to be doing a lot of statistics, you should take a few courses and also learn a package such as R. The alternative is to hire a statistician.