I think that I can safely say that most Christians don’t believe in the Bible. But let me qualify this statement. Most Christians don’t believe in all of the Bible, or even most of it. I say this because most Christians don’t know what the Bible says because they haven’t sufficiently studied it.
By Christian I mean anyone who self identifies as a Christian. The only way to know for sure if someone considers themselves to be a Christian, or a Jew, or a Muslim, or a Hindu is to ask them. Sometimes it is obvious from their dress, or the situation, or surroundings, or their actions. But we usually have to ask them to know for sure.
The only way to get to know God is through the Bible. Some Christians believe they can directly communicate with God. But most Christians have to rely on the Bible. And most Christians don’t take the time to know and understand the Bible either because either they don’t believe it is the word or God, or they don’t actually believe in the Christian God.
Actions are a better indicator of our beliefs than the words we speak. Most people who self identify as a Christian don’t act like someone who believes in the Bible.