School counselor claims that the average number of sleep students get each night is 6 hours. A researcher has taken a well–designed survey and his sample mean is 8.5 hours and sample standard deviation is 0.25. The sample size is 400. Which statement is correct?

a.)
The result of the survey is not statistically significant.
b.)
The difference exists due to chance since the test statistic is small.
c.)
The sample size should be much more.
d.)
The result of the survey is statistically significant.