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.
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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.
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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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