9.62 A consumer agency has retained an independent testing firm to examine a tel

Question

9.62 A consumer agency has retained an independent
testing firm to examine a television manufacturer’s claim
that its 25-inch console model consumes just 110 watts of
electricity. Based on a preliminary study, the population
standard deviation has been estimated as 11.2 watts for
these sets. In undertaking a larger study, and using a simple
random sample, how many sets must be tested for the firm
to be 95% confident that its sample mean does not differ
from the actual population mean by more than 3.0 watts?

Explanation / Answer

n = (z^2 * s^2) / c^2 n = (1.96^2 * 11.2^2) / 3^2 n = (3.8416 * 125.44) / 9 Answer: n = 53.54 (54)

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