Question

8. The batteries produced in a manufacturing plant have a mean time to failure of 30 months, with a standard deviation of 2 months. I select a simple random sample of 400 batteries produced in the manufacturing plant. I test each and record how long it takes for each battery to fail. I then compute that the average failure time of the 400 batteries is 29.9 months with a standard deviation of 2.15 months. In this scenario, the value 29.9 is:

   A) μ and it is a statistic B) x and it is a statistic C) μ and it is a parameter D) x and it is a parameter

9. Which of the following description of the standard error of the mean is correct?

   A) The standard error of the mean is the standard deviation of the sampling distribution of the mean B) The standard error of the mean is the squared variance of the sampling distribution of the mean C) Standard error is the sample standard deviation D) Standard error is the same with population standard deviation

   1. As the sample size increases, the standard deviation of the sample distribution of the mean will:

      A) Increase
      B) Decrease
      C) First increase then decrease D) First decrease then increase

   2. According to the Central limit theorem, as the sample size___, the sample distribution of the mean is closer to ___.

      A) Increases; the population distribution B) Decrease; the population distribution C) Increase; a normal distribution
      D) Decrease; a normal distribution

Answer 1

B) x and it is a statistic

A) The standard error of the mean is the standard deviation of the sampling distribution of the mean

As the sample size increases, the standard deviation of the sample distribution of the mean will: B) Decrease

According to the Central limit theorem, as the sample size increases C) Increase; a normal distribution