A certain brand of automobile tire has a mean life span of 39,000 miles and a standard deviation of 2,450 miles. (Assume the life spans of the tires have a bell-shaped distribution.)
(a) The life spans of three randomly selected tires are 35,000 miles, 36,000 miles, and 31,000 miles. Find the Z-score that corresponds to each life span.
For the life span of 35,000 miles, Z-score is -1.63.
(Round to the nearest hundredth as needed.)
For the life span of 36,000 miles, Z-score is - 1.22
(Round to the nearest hundredth as needed.)
For the life span of 31,000 miles, Z-score is - 3.27
(Round to the nearest hundredth as needed.)
According to the Z-scores, would the life spans of any of these tires be considered unusual?
No
Yes
(b) The life spans of three randomly selected tires are 34,100 miles, 43,900 miles, and 39,000 miles. Using the empirical rule, find the percentile that corresponds to
each life span
The life span 34,100 miles corresponds to the ? Ith percentile.
The life span 43,900 miles corresponds to the th ?percentile.
The life span 39,000 miles corresponds to the th ?percentile.
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