Answer to Question #2861 in Statistics and Probability for Dishen Patel

Question

Refer to problem BELOW. Belkin Products obtained 18 observations of the output voltages for a particular power supply unit. For these data, while solving problem 2) above, you have obtained (the point estimate of µ) and s (the point estimate for ¬). Now, for problem 3), how large a sample would the firm need for to be within .2 volts of the actual average output voltage with 95% confidence?


The output voltage of power supplies manufactured by Belkin Products is believed to follow a normal distribution. Of primary concern to the firm is the average output voltage of a particular power supply unit, believed to be 10 volts. Eighteen observations taken at random from this unit are as given below:

10.85, 11.40, 10.81, 10.24, 10.23, 9.49, 9.89, 10.11, 10.57, 11.21, 10.10, 11.22, 10.31, 11.24, 9.51, 10.52, 9.92, 8.33

What is the 95% confidence interval for the average output voltage for this power supply unit?