Trendline (IM 573)

There is this saying that goes :- "If today is a sunny day then there is a 80 % chance that tomorrow will be a sunny day as well." There will of course be a certain trendline then can in some way predict tomorrow. And it might have 80% chance of being true depending on how precise and certainty the prediction is. We can see this in stock market, where various trendline and moving averages are used to predict upcoming market movements.