Some of this may be cultural (both cultural to the country you are in or to the organization) and some may be that you are new and have not yet developed a reputation as someone who can provide answers.
The first step is to talk to your manager about the workplace culture and determine if the reason why they are going to him directly is simply the way that company/country does business. If this is the case, then you need to simply accept that this indirect approach is the way things are done and work with your boss to make sure he has the information at his fingertips to answer their questions. It never harms you in the workplace to make sure your boss looks good.
Also in this case, take notes about how he answers questions and which ones he defers for later. You can still learn how things are handled even if you are not the one answering the questions. Work out a method with him where you can pass information on to him quietly if he appears to be going in a wrong direction. Some bosses might want you to pass them a note with the further information, some might want to let it wait until after the meeting and some might expect you to jump in the discussion with the additional information.
If the boss thinks there is a problem with how you are presenting the information or with your work, then this discussion will likely bring that out too. This is good to know as you can't fix a problem until you know what it is. If he is answering because he does not trust you to have the answer or trust that you know how to deal with the politics of the situation, you need to find out exactly what actions you need to take to improve your performance and build trust with your supervisor. These actions are likely to be workplace specific.
When I was young, I sat down with my boss and had a few training sessions where he pretended to be the person who would ask questions in a meeting (eventually getting quite aggressive or hostile) and let me answer them and get tips on better ways to respond. Once he was sure I could handle the questions, he was able to let me handle more things in a group setting. You could ask to get this type of training if he is not sure you can handle yourself if things get heated.
You could also clarify with him what type of questions he should start giving you to handle and what he needs to to keep at his level. If you can get his reasoning on this, you will be learning more about how that workplace works and the politics of the situation which is critical for anyone who deals with data analysis (this is my professional specialty so I know).
If, as seems most likely since you are new, the issue is simply that they don't trust your well enough to ask you directly, then you need to work with your boss to help gain their trust.
First, start by delivering excellent work on time. Getting a reputation for delivering the goods is the fastest way to becoming respected and to them then going to you.
You could consider asking about when you can start to handle some of the less controversial meetings without his presence. They will be more likely to ask you questions directly if he is not there. Work out with your boss what types of questions are your responsibility to answer under these circumstances and which (generally those relating to policy changes and schedule and priority) you will need to refer to him. If he does let you handle some less important meetings, be sure to let him know in an email what questions were asked and how you handled them and any questions that you deferred to him (As they may not get around to asking the of him directly).
You can consider asking your boss, to verbally pass the question to you in the presence of these people. Having the support of your boss and his trust that you can handle the question is another good way for people to realize that you are to be trusted.
Be aware though that some supervisors are not willing to give up their perceived power by passing things to you publicly. In this case, making sure he has the information he needs to make both of you look good is your best choice. If he looks good enough, he will likely get promoted out of your hair. If you have given him the support he needs to look good, He may well recommend you for promotion to his position when he leaves. Even an overly micromanagement boss can be someone you can learn from. Again take notes as to how he answers questions and how he deflects things he is not ready to answer at that moment. Even if you are no doing the answering, you can learn how more senior people deal with questions.