okay i am stuck on this one.

a recent study in a city stated that the average of retired men was 63.5 years. A sample of 20 retirees had a mean of 63.7 and a standard deviation of 1.9. At alpha = .05 is the average age higher than originally believed? Use the p-value method.

ho u = 63.5

h1 u not = 63.5

63.7 - 63.5

______________

1.9/ sqrt of 20

i got .471

but that is not on the t distribution table, this is where i am stuck , i am trying to see what the book says, but i get lost.