A new investor only needs to believe in bitcoin after checking the price history of bitcoin and see that the price of bitcoin going up in future has high odds than it going down because bitcoin is still going to mature more and more overtime.
No, i don't expect an investor to believe in Bitcoin by just checking the price of Bitcoin in the past or currently. He must understand the nature of Bitcoin, and grasp knowledge from it. Only then he will have his personal conviction on Bitcoin and believe in it. The price being assured to go up for years than going down is what build trust to choose it as the best asset to invest in. But believing is witnessing. When we start to invest with the knowledge we have and things start working out properly based on our goals, strategies and longevity then we are not true believers because we would rather trust in holding it for more than 10 years rather than trusting it in the short term
I guess that doesn't mean about solely checking the price then try to believe it, but rather make those past price achievement reached by bitcoin as good basis to believe that bitcoin really has a potential to grow and those who engage earlier are now gaining good figures as of the moment. Those events is already a good basis for people to believe that there's something more if they going to invest with bitcoin for long term purposes.
What usually been promoted now is trading especially if you learn information about bitcoin in other social media platforms. That's why its good to correct those negative thoughts that there is a something more better investment option which posses low risk if they just explore more other earning opportunity what bitcoin could able to give them. 4 - 10 year length is ideal for them since with that time span for sure that they can able to get good profits with bitcoin.