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2. (5’) A manufacturer claims that a certain brand of VCR player
has an average life expectancy of 5 years and 6 months with a
standard deviation of 1 year and 6 months. Assume that the life
expectancy is normally distributed.
(a) Selecting one VCR player from this brand at random,
calculate the probability of its life expectancy exceeding 7
(b) The Critical Consumer magazine decides to test fifty
VCRS of this brand. The average life in this sample is 6
years and the sample standard deviation is 2 years.
Calculate a 99% confidence interval for the average life.
(0) How many more VCRs would the magazine have to test
in order to halve the width of the confidence interval

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