Need help with correct answers

You are considering purchasing a coin operated laundry in a neighborhood. The previous owner claims that the average revenues from the laundry exceed $750 per day. You agree to purchase the laundry only if you feel confident that the laundry s revenues exceed $750 per day. You gather revenue data on 120 randomly selected days, and obtain a sample mean of $785, with a standard deviation of $95. At= .01, would you still purchase the laundry?

a	The Null Hypothesis for this problem is that Revenues are $750.00 with an Alternate Hypothesis is that Revenues > $750. I will not be able to reject the Null Hypothesis since my calculated Z is greater than my critical Z* of 4.035. Therefore, I will purchase the laundry
b	The Null Hypothesis for this problem is that Revenues are $750.00 with an Alternate Hypothesis is that Revenues < $785. I will not be able to reject the Null Hypothesis since my calculated Z is greater than my critical Z* of 4.035. Therefore, I will not purchase the laundry
c	The Null Hypothesis for this problem is that Revenues are $785.00 with an Alternate Hypothesis is that Revenues > $750. I will reject the Null Hypothesis since my calculated Z is greater than my critical Z* of 4.035. Therefore, I purchase the laundry
d	The Null Hypothesis for this problem is that Revenues are $750.00 with an Alternate Hypothesis is that Revenues > $750. I will reject the Null Hypothesis since my calculated Z is greater than my critical Z* of 2.33. Therefore, I will purchase the laundry

C

Which of the following statements are correct when deciding whether to use thezor thetdistribution?

a	Usezwhen the sample size is 30 or more.
b	Usezwhen we have a normal population and we know the standard deviation.
c	Usetwhen the population is normal, the population standard deviation is not known, andnis less than 30.
d	All of the above statements are correct.

C

A manufacturer of spark plugs claims that its plugs have an average life in excess of 23,000 miles. The fleet owner purchased 18 sets and found that the sample average life was 23,400 miles, the sample standard deviation was 750 miles. Based on these findings, there is enough evidence to accept the manufacturer's claim at the 0.005 level.

a.	This claim is reasonable because we are not able to reject the null, since the critical T* is less than the Calculated T of 2.2627
b.	This claim is false because we reject the null hypothesis, since the Calculated T of 1.875 is greater than the Critical T
c.	This claim is supported because we reject the null hypothesis, since the Calculated T 2.2627 is greater than the Critical T

d.

This claim is false because we are not able to reject the null hypothesis, since the Calculated T of 2.262 is less than the Critical T C My Calculation? H0: mu = 23000 and Ha: mu > 23000 n = 18, x-bar = 23400, s = 750 SE = s/sqrt n = 750/sqrt 18 = 176.77 Right-tailed t- test; a = 0.05, Dof = 17, Critical t- score = 1.74 Decision Rule: Reject H0 if t- score for the sample > 1.74 t = (x-bar - mu)/SE = (23400 - 23000)/176.77 = Since 2.2628 > 1.74, we reject H0 and accept Ha Conclusion: The manufacturer's claim that mu > 23000 miles is valid.

In multiple regression, a dummy variable can be included in a multiple regression model as

a	An additional quantitative variable
b	A nominal variable with three or more values
c	A nominal variable with only two values
d	A new regression coefficient

A