A Random Sample of 121 Checking Accounts at a Bank

question 121

Essay

A random sample of 121 checking accounts at a bank showed an average daily balance of $280.The standard deviation of the population is known to be $66.
a.
Is it necessary to know anything about the shape of the distribution of the account balances in order to make an interval estimate of the mean of all the account balances? Explain.
b.
Find the standard error of the mean.
c.
Give a point estimate of the population mean.
d.
Construct an 80% confidence interval for the population mean.
e.
Construct a 95% confidence interval for the population mean.

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Definitions:

Gross Profit

The difference between sales revenue and the cost of goods sold, indicating the profitability of a company's core activities.

Operating Expenses

Costs incurred during the normal course of business operations, excluding the cost of goods sold.

Income from Operations

Earnings generated from a company's regular, core business activities before interest and taxes.

Gross Profit Percentage

A financial metric expressing the gross profit as a percentage of net sales, showing the efficiency of a company in making and selling its products.