there is a correlation between price and hashrate but not the way it has been advertised by some newbies on the internet for the past year. the correlation is simply this: if price goes up, hashrate follows and if price goes down hashrate can follow. but if hashrate rises or falls it doesn't affect the price.

think of it this way, miners are employees that are hired to do a job for the bitcoin network and get paid for the amount of job they do. imagine if you were an employee of a company that paid you $50 per hour of work you perform and you could work 1 hour a day or 10 if wanted to. if you some day decide to leave the company (lower hashrate) the company doesn't go down or they won't reduce the salary they pay, instead they simply hire someone else to fill your place.
that is what happens if hashrate drops. suddenly room opens up for other miners to come in and make profit so hashrate goes back up again. in reality since there are thousands and thousands of miners there isn't any sudden big rise or drops. instead there is fluctuations.