the interval X these bearings. 1.645σ /?n, where σ XX is assumed to be known from past experience with
An engineer plans to compute a confidence interval on the true mean inner diameter of the
bearing used to support the crankshaft of a particular engine. She will do this by measuring the ̄
inner diameters of a random sample of these bearings, compute X and, and then computing ̄
?
the interval X these bearings.
1.645σ /?n, where σ XX
is assumed to be known from past experience with
-
a) The confidence interval that she is computing has what probability that the true mean diameter will be included?
-
b) Suppose that the following measurements were recorded, in mm,
30.003, 30.004, 29.998, 30.001, 29.996, 30.002
If σX is known from past experience to be 0.003 what is her confidence interval? -
c) If the standard deviation is not known, what now would be her confidence interval?
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