The distribution of claim size for a car insurance company in 2007 was normally distributed with a mean of $1200 and a standard deviation of $240. A random sample of 50 claims made in the year 2008 yielded a mean of $1150. Test whether the population mean claim has decreased using = 0.05.

**I got the correct answer, I just cant remember how I reached the answer.

I must be missing a step. Can you post step by step?