Actually, your question begins to make a lot of sense if you extend it by one generation, and ask what deviation from the average of 25% of genetic material people receive from their grandparents.  
 As each parent themselves have a mixture of 50% each from their parents, and meisosis mixes this up during the time between conception of the parent and conception of the child, you will get very close to 25% contribution from each grandparent, but there may be  deviations. I assume you would expect a poisson distribution for that, so on average 5% deviation from the 25%, so most people will have between typically 20% and 30% from each grandparent. The poission distribution will be almost gaussian due to the large number of genes, but for this, you may actually go and look for studies verifying it.