Highway Speefs Listed below are speeds (mi/h) measured from southbound traffic on I-280 near Cupertino, California (based on data from Sig Alert). This simple random sample was obtained at 3:30 p.m. on a weekday. Use the sample data to construct a 95% confidence interval estimate of the population standard deviation. Does the confidence interval describe the standard deviation for all times during the week?
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Assume that each sample is a simple random sample obtained from a population with a normal distribution.