Suppose that a certain website claims that it averages 4.7 hours of downtime per month. (Downtime is time that the site is not available.) 
In a random sample of 17 months, the average downtime was 4.9 hours per month, with a standard deviation of 0.5 hours per month. What is the z-value rounded to the nearest hundredth?  Is there enough evidence to reject the claim?​