In the example presented in video, market analyst was asked to check if email open rate of competitors is above 40%. So according to previous lectures, null hypothesis should be the one which we test and we assume "current state" as null hypothesis. According to this logic, null hypothesis should be Ho >= 40%. But video says null hypothesis is Ho<= 40%. I could not understand this. Please clarify and if possible point me to other material where I can find how to choose null and alternate hypothesis.

Hello Vipin! Thanks for reaching out! Here, we want to estimate if the competitor has a higher rate. This basically tells you the alternative hypothesis. Usually, what you try to achieve or prove is what drives the alternative hypothesis. If we cannot reject the null hypothesis, it means we have been wrong and the competitor has the same or lower email rate. Best, The 365 Team