a lil' more help

[hilarysears77]

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.

[JohnM]

Hilary,

This is a directional hypothesis (the use of the word "higher" or "lower" in the question is the tip-off)

Ho: mu = 63.5
Ha: mu > 63.5

compute t = (63.7 - 63.5) / (1.9 / sqrt(20))
= .471

You don't need to look up .471 in the t-table --> you just need to look up the critical value of t for alpha=.05 and dof = 19, and determine whether or not .471 is in the rejection region or acceptance region.