How to find a 95 percent confidence interval for a specifc price

[colestech23]

proc ttest data = stock_price alpha = .05;
var price = 2.58; *would it be 2.58 if task was 2 in the data ? ; 
run;

[ballardw]

What are you attempting to do? Determine if the mean price is 2.58? Is different from 2.58?

You could test a null hypothesis that the mean is a given value with the H0= option on proc ttest statement:

Proc ttest data=stock_price alpha=.05 H0=2.58;

Task?  What is task?