12. 9-1-1 Samples of 100 8-hour shifts were randomly selected from the police records for each of two districts in a large city. The number of police emergency calls was recorded for each shift. The sample statistics are listed here:

Find a 90% confidence interval for the difference in the mean numbers of police emergency calls per shift between the two districts of the city. Interpret the interval.

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Region 1 2 Sample Size 100 100 Sample Mean 2.4 3.1 Sample Variance 1.44 2.64