Statistic
posted by Marilyn .
A restaurant that bills its house account monthly is concerned that the average monthly bill exceeds $200 per account. A random sample of twelve accounts is selected, resulting in the sample mean of $220 and a sample standard deviation of $12. The researchers have determined that they should test that the mean bill exceeds $200 at the 5% level of significance.
What is the Null Hypothesis?
What is the Alternate Hypothesis?
How many tail(s) in the test?
What test should the researchers use?
Why do they use this test?
What is the critical value?
If the calculated value for the test statistic is 5.77, then what have the researchers learned with the test?
Are the test results reliable?

n: 12
Mean: 220.00
SD: 12.00
α: 0.05
H0:<=200 H1:>200
Reject H0 if t > 1.796
t=(220.00  200.0)/(12.00/sq 12)
t= 20.00 / 3.46
t= 5.77
Reject H0 because t value is greater than 1.796