1. The mean balance of all checking accounts at a bank on December 31, 2009, was $850. A random sample of 41 checking accounts taken recently from this bank gave a mean balance of $780 with a population standard deviation of $230. Using the 1% significance level, can you conclude that the mean balance of such accounts is different during this period? Explain your conclusion in words.
2. A random sample of 20 acres gave a mean yield of wheat equal to 41.2 bushels per acre with a standard deviation of 3 bushels. Assuming that tpopulation distribution is rightward skewed, Construct a 90% confidence interval for the population mean. Draw graph