You are given the following information obtained from a random sample
of 5 observations. 20 18 17 22 18

At 90% confidence, you want to determine whether of not the mean of
the population from which this sample was taken is significantly less
than 21. Assume a normal distribution of the population.

a) state the null and alternative hypothesis.
b) compute the standard error of the mean..
c) determine the test statistic
d) test to determine whether or not the mean of the population is
significantly less than 21.

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Clarification of Question by cecilathome-ga on 07 Aug 2002 21:04 PDT

No they are not - they are study questions in preparation for a test. 
As you can see by my previous posts - I'm attempting to work out the
answers at the same time.  I was using the responses as validation of
my work and as question by question tutoring...

The appropriate calculator is at
  http://www.seeingstatistics.com/seeing1999/gallery/TTest.html