The metrics I mentioned are mainly used in civil actions, not criminal actions, because civil actions tend to be a lot more complicated, whether it is because they raise constitutional issues, business issues, or novel issues of law. In such cases we care about indicators that may suggest you would not either be able to understand the issues or follow the arguments or that your particular background would suggest you would make your determination from unspoken prejudice rather than by objectively interpreting the available facts in light of the arguments raised. The indicators tend to be sociological in nature and vary from case to case, depending on the issues. A juror's job is to merely decide the issues of fact, not law, but sometimes the prejudices we all have can interfere with that necessary objectivity.
I'll give an example. Suppose a case turns on a very complex issue of fact. If you side would most likely win if the juror completely understands the argument but most likely lose if the juror doesn't, you are going to want all the scientists and economists and doctors you can pack on that jury and you may shy away from truck drivers and home health care assistants. That may not be fair and you could even shoot yourself in the foot, depending on the individual involved, but all you can do is go with the odds. The metrics say that people who regularly deal with complex and abstract issues are more likely to be swayed by your arguments, though once again there is more involved.
The other reason selecting jurors is more of an art in civil matters is that in civil actions matters are decided by a majority determination of more likely than not rather than a unanimous decision of beyond a reasonable doubt, though that unanimity in high profile cases like the Jimmy DiMora case or the OJ Simpson case means that all the defense needs to do is to sway one juror, further meaning to the degree the defense can mount arguments that could appear reasonable, they care very much about each individual juror. The other thing we typically look for in criminal cases is the juror who has enough in common with the accused that they could identify with him or her and not find him or her guilty for that reason rather than fully consider the facts. Obviously the defense wants that juror and the prosecution not. This happens mostly in white collar cases or sometimes in matters involving "victimless" crimes. (If a dumpy male divorced factory worker with not much of a life is being tried for soliciting a prostitute after a long night at a bar and you indicate you are a dumpy male divorced factory worker without much of a life who sometimes spends long nights in bars, you are probably going to be excused by the prosecution just to be safe.)
Conversely, when you are called to jury duty here in the state courts, probably 95% of the juries are seated for common criminal cases, so mostly all we care about is the potential juror likely being reasonable and intelligent enough to understand the issues, which are almost always pretty basic. If you don't want to sit on a jury, do as the fellow did in a previous comment in this thread, give the judge reason to believe you are incapable of being relied upon to deliver an honest assessment of guilt. You will be excused, partly because the judge recognizes the problem, partly because seating such a juror could be a reason for appeal.
Sometimes jurors send this message inadvertently without realizing it. If you have questionable views that are so far out of the mainstream that would suggest you could not be relied upon to return a fair verdict, you would likely be excused. That does not generally include atheism per se around here, but there are other things that will send up red flags. Tell the judge you are a Nazi or a Satanist or something similar and you may find yourself going home, fairly or not.