Utility Bill

1. (TCO 8) For the following statement, write the null hypothesis and the alternative hypothesis. Also label which one is the claim.
Company X claims that the average salary for an entry level employee is $35,000 (Points : 8) 

2. (TCO 11) A pizza restaurant manager claims that the average home delivery time for their pizza is no more than 25 minutes. A random sample of 49 home delivery pizzas was collected. The sample mean was found to be 26.5 minutes and the standard deviation was found to be 4 minutes. Is there evidence to reject the manager’s claim at alpha =.05? Perform an appropriate hypothesis test, showing the necessary calculations and/or explaining the process used to obtain the results. (Points : 20) 

3. (TCO 5) At a jewelry store, the probability for a customer to make a purchase when entering the store is 35%. We asked 25 customers enter the store whether they made a purchase or not.
(a) Is this a binomial experiment? Explain how you know.
(b) Use the correct formula to find the probability that, out of 25 customers, exactly 10 of them make a purchase. Show your calculations or explain how you found the probability.
(Points : 20) 

4. (TCO 6) The monthly utility bills are normally distributed with a mean value of $150 and a standard deviation of $20.
(a) Find the probability of having a utility bill between 135 and 170.
(b) Find the probability of having a utility bill less than $135.
(c) Find the probability of having a utility bill more than $180. (Points : 20) 

5. (TCO 8) A Mall manager claims that in average every customer spends $52 per a single visit to the mall. To test this claim, you took a sample of 36 customers and found the sample mean to be $55 and the sample standard deviation to be $12. At alpha = 0.05, test the Mall’s manager claim. Perform an appropriate hypothesis test, showing the necessary calculations and/or explaining the process used to obtain the results. (Points : 20) 

6. (TCO 7) A bank manager wanted to estimate the mean number of transactions businesses make per month. For a sample of 50 businesses, he found the mean number of transaction per month to be 35 and the standard deviation to be 9.5 transactions.
(a) Find a 99% confidence interval for the mean number of business transactions per month. Show your calculations and/or explain the process used to obtain the interval.
(b) Interpret this confidence interval and write a sentence that explains it. (Points : 20) 

7. (TCO 7) A company’s CEO wanted to estimate the percentage of defective product per shipment. In a sample containing 600 products, he found 45 defective products. 

(a) Find a 99% confidence interval for the true proportion of defective product. Show your calculations and/or explain the process used to obtain the interval.
(b) Interpret this confidence interval and write a sentence that explains it. (Points : 20) 

8. (TCO 2) The ages of 10 students are listed in years:{ 17,22,19,24,21,23,29,18,22,28 }
 

(a) Find the mean, median, mode, sample variance, and range.
(b) Do you think that this sample might have come from a normal population? Why or why not? (Points : 20)