question archive 1 The finance manager of a Woolworth claims that the mean balance for the store's charge account customers is N$510
1 The finance manager of a Woolworth claims that the mean balance for the store's charge account customers is N$510
Subject:StatisticsPrice: Bought3
1 The finance manager of a Woolworth claims that the mean balance for the store's charge account customers is N$510. An independent auditor from PWC selects a random sample of 45 accounts and finds a mean balance of N$511.33 and a standard deviation of N$103.75. If the manager's claim is not supported by these data, the auditor intends to examine all charge account balances. Question: Formulate the Null and Alternative Hypothesis for this problem.
2 points
a) H0: μ1≠510 vs H1: μ1=510
b) H0: μ1=510 vs H1: μ1≠510
c) H0: μ1≥510 vs H1: μ1<510
d) H0: μ1≤510 vs H1: μ1>510
2 Using the information provided in the previous question, calculate the z-statistic using the z-test and tick the correct answer.
5 points
a) z-statistic = 0.0860
b) z-statistic = 0.0341
c) z-statistic = 2.3401
d) z-statistic = 2.1961
3 Based on your empirical evidence in the previous question and using a 5% level of significance, make a statistical conclusion and tick the correct answer below.
2 points
a) Accept the alternative because the statistic is very small.
b) Fail to reject the Null hypothesis, the alternative is probably false.
c) None of these answers is correct.
d) Reject the Null hypothesis. The alternative is probably true.
4 A human resources director at the Namibia Chamber of Mines wishes to estimate the true mean employment period of all Uranium miners. From a random sample of 144 Uranium miners' records, the sample mean employment period was found to be 88.4 months. The population standard deviation is assumed to be 21.5 months and normally distributed. Question: Find the 95 % confidence interval estimate for the actual mean employment period (in months) for all miners employed in uranium mines.
4 points
a) The actual mean employment period (in months) for all miners employed in uranium mines lies between 83.45 and 90.52.
b) The actual mean employment period (in months) for all miners employed in uranium mines lies between 84.89 and 91.91.
c) The actual mean employment period (in months) for all miners employed in uranium mines lies between 85.45 and 91.34.
d) The actual mean employment period (in months) for all miners employed in uranium mines lies between 85.01 and 91.62.
5 A Spar retailer observed a random sample of 161 customers and found that 69 customers paid for their grocery purchases by cash and the remainder by credit card. Question: Construct a 90% confidence interval for the actual percentage of customers who pay cash for their grocery purchases.
5 points
a) The actual percentage of customers who pay cash for their grocery purchases lies between 42.81% and 43.90%.
b) The actual percentage of customers who pay cash for their grocery purchases lies between 36.44% and 49.28%.
c) The actual percentage of customers who pay cash for their grocery purchases lies between 42.12% and 41.80%.
d) The actual percentage of customers who pay cash for their grocery purchases lies between 37.85% and 47.87%.
