Question

A small manufacturer of LCD television displays is seriously concerned about the quality of his product. Recent reports from owners seem to indicate that life expectancy of these displays has fallen far short of the advertised figure given to the retailers. A research analyst is called in to conduct a study to investigate the truth of these charges.The average life expectancy figure given to retailers was 1000 hours per display. The analyst, therefore, decides to investigate the population mean life of all displays produced by the company. The null and alternate hypotheses he plans to test appear below.

Ho: ? ? 1000
Ha: ? < 1000

He next selects a random sample of 81 displays and subjects each to a series of intricate tests whereby the useful life of each dsplay is estimated.The results for this sample indicate the mean useful life of a dsplay was 960 hours. The population standard deviation of the hours of dsplay life is known to be 225 hours.

Suppose the appropriate critical region for the test is a mean value that is less than or equal to 950 (actually it is not). What is the outcome of the test of the null hypothesis?

		Retain Ho
		Retain Ho and accept the mean is less than 1000
		Reject Ho and accept the mean is greater than 1000
		Reject Ho and accept the mean being less than 1000

Answer 1

Since the mean value is greater than 950, Retain H₀.

Option - A is correct.