Question

1. Using n – 1 in the denominator for the sample variance is a much better...

1. Using n – 1 in the denominator for the sample variance is a much better estimate of the true population variance when compared to dividing by n.

True

False

2.

During the 3 pm to 5 pm time period, cars arrive at a bank's drive-through window at an average rate of 15 customers per hour. Assume that the time between arrivals follows the exponential distribution. What is the standard deviation for this probability distribution?

a.

2 minutes
b.

4 minutes
c.

1 minutes

d. 10 minutes

3.

The average battery life of the iPhone is reported to be 7.0 hours. Assume that the standard deviation for the battery life for this cell phone is 45 minutes. A random sample of 38 iPhones had an average battery life of 6.5 hours. Which of the following statements is correct?

The interval that contains 95% of the sample means is 5.50 and 8.50 hours. Because the sample mean is between these two values, we do not have support that the average battery life equals 7.0 hours.

The interval that contains 95% of the sample means is 5.50 and 8.50 hours. Because the sample mean is between these two values, we have support that the average battery life equals 7.0 hours.

The interval that contains 95% of the sample means is 6.76 and 7.24 hours. Because the sample mean is not between these two values, we have support that the average battery life equals 7.0 hours.

The interval that contains 95% of the sample means is 6.76 and 7.24 hours. Because the sample mean is not between these two values, we do not have support that the average battery life equals 7.0 hours.
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