Probability that one randomly selected pair of batteries

Reference no: EM13177725

A popular flashlight that uses two D-size batteries was selected, and several of the same models were purchased to test the "continuous-use life" of D batteries. As fresh batteries were installed, each flashlight was turned on and the time noted. When the flashlight no longer produced light, the time was again noted. The resulting "life" data from the batteries had a mean of 21.3 hours. Assume these values have a normal distribution with a standard deviation of 1.42 hours. (Round your answers to four decimal places.)

(a) What is the probability that one randomly selected pair of batteries will have a test life between 20.8 and 21.8 hours?
(b) What is the probability that a randomly selected sample of 4 pairs of batteries will have a mean test life between 20.8 and 21.8 hours?
(c) What is the probability that a randomly selected sample of 15 pairs of batteries will have a mean test life between 20.8 and 21.8 hours?
(d) What is the probability that a randomly selected sample of 66 pairs of batteries will have a mean test life between 20.8 and 21.8 hours?
(e) Describe the effect that the increase in sample size had on the answers for parts (b)-(d).
Select the correct answer:
A. As sample size increased, the standard error increased, resulting in higher probabilities.
B. As sample size increased, the standard error increased, resulting in lower probabilities.
C. As sample size increased, the standard error decreased, resulting in higher probabilities.
D. As sample size increased, the standard error decreased, resulting in lower probabilities.

Reference no: EM13177725

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