Question 601612
For the problem below, I've solved the df (49.77) and the t value (-2.84), but am unsure about the critical value. 
Businesses, particularly those in the food preparation industry such as General Mills, Kellogg, and Betty Crocker regularly use coupons as a brand allegiance builder to stimulate their retailing. There is uneasiness that the users of paper coupons are different from the users of e-coupons (coupons disseminated by means of the Internet). One survey recorded the age of each person who redeemed a coupon along with the type (either electronic or paper). The sample of 35 e-coupon users had a mean age of 33.6 years with a standard deviation of 10.9, while a similar sample of 25 traditional paper-coupon clippers had a mean age of 39.5 with a standard deviation of 4.8. Assume the population standard deviations are not the same.
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Using a significance level of 0.01, test the claim that e-coupon users are younger than traditional-paper coupon users.
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That last sentence implies you have left-tail test with alpha = 1%
Critical value: t = invT(0.01,49.77) = -2.4036
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I used a TI-84 to get that t-value.
Cheers,
Stan H.
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