Hypothesis testing with sigma unknown...help?

[Claraoswald]

I understand how to do the testing with sigma known, but I don't understand how/when to use the T-table for this.

The problem: "It is stated that the average person commutes 21 miles to work. You go out and randomly sample 64 people and get a sample average of 20 miles with a sample standard deviation of 6 miles. You'd like to test the accuracy of this claim of the level of significance of 0.05."

I know you're trying to prove the claim otherwise. How do I do that?

 

[Ishuda]

I understand how to do the testing with sigma known, but I don't understand how/when to use the T-table for this.

The problem: "It is stated that the average person commutes 21 miles to work. You go out and randomly sample 64 people and get a sample average of 20 miles with a sample standard deviation of 6 miles. You'd like to test the accuracy of this claim of the level of significance of 0.05."

I know you're trying to prove the claim otherwise. How do I do that?

I don't always do well at sadistics so I found this 't test for dummies' a pretty good read
http://www.dummies.com/how-to/content/how-to-use-the-ttest-to-handle-small-samples-and-u.html