Statistics 203A Midterm Exam II – November 9, 2010 Name: ___KEY____ Instructions: ID No. ___________ 1. Closed books/notes examination except that you may use a one page of notes written on both sides. 2. Attempt all questions and leave your answers in the space provided. [32] Total Marks (Time: 60 minutes)

Question 1 [True-or-false Questions: 12 marks]

1-1. 1-2.

T F (1 mark) If X is a normally distributed random variable with a mean of 80 and a standard deviation of 12, then the P(X = 68) is 0. T F (1 mark) A city is subdivided into districts, each of which is similar in characteristics to the whole city. A SRS of these districts is chosen and a SRS is chosen from each of these districts. This is an example of cluster sampling. T F (1 mark) You plan to construct a 99% confidence interval for the mean m of a normal population with (known) standard deviation s. By using a sample size of 400 rather than 100, you can reduce the margin of error by a factor of 4. (4!2) T F (1 mark) SD is larger than IQR in the standard normal distribution. (SD =1 and IQR =1.35) T F (1 mark) The 10th percentile is for the standard normal distribution approximately 1.28. (1.28!-1.28) T F (1 mark) The standard deviation of a sampling distribution of means is larger than the standard deviation of the population. Larger !Smller T F (1 mark) The mean of a sampling distribution of means (the mean of means) is equal to the true population mean. T F (1 mark) With