SOLUTION: Could someone please tell me if these answers are correct - thanks According to a 2003 report, in California Chocko Chip Cookie sales have a mean of $1323 per week. Suppose that a

Question 962940: Could someone please tell me if these answers are correct - thanks
According to a 2003 report, in California Chocko Chip Cookie sales have a mean of $1323 per week. Suppose that a random sample of 30 weeks in 2009 in the same stores showed that Chocko Chip Cookies were selling at a mean rate of $1208 with a sample standard deviation of $275. Does this sample indicate that the sales of Chocko Chip Cookies is different from the earlier figure?
(A) Write the null and alternative hypothesis.
Ho: u=1323 H1: u does not equal 1323
(B) Determine the critical values
Two-tailed test +/-
(C) Calculate the test statistic
1208-1323/275/sqrt30 = -2.290
(D) Decide whether to reject or accept the null hypothesis
Do not reject
(E) Write a full conclusion
The mean salesof Chocko Chip Cookies is not significantly different from
$1323

Answer by rothauserc(4718) (Show Source): You can put this solution on YOUR website!
(A) H1: u is less than 1323 or greater than 1323
(D) It is common to use a 5 percent probability level for the test to reject the Ho and since we must consider statistical difference below and above the mean we use .05/2, that is the rejection region must be split between both tails of the distribution�0.025 in the upper tail and 0.025 in the lower tail�because your hypothesis specifies only a difference.
**************************
The critical z‐scores for a probability of 0.025 in either tail to be �1.96 and 1.96. In order to reject the null hypothesis, the test statistic must be either smaller than �1.96 or greater than 1.96.
**************************
The z-score for 1208 is -2.290 which is lower than the z-score of -1.96 so we would reject the Ho. Again, this test uses the 5 percent probability since your problem does not include a statement of the probability level.
(E) The sample mean is statistically different from 1323.
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