SME_8e_Ch_09_Section_3 - CHAPTER 9 SECTION 3: SAMPLING...

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1 CHAPTER 9 SECTION 3: SAMPLING DISTRIBUTIONS MULTIPLE CHOICE 136. If two populations are normally distributed, the sampling distribution of the difference in the sample means, X 1 - X 2 , is: a. approximately normal for any sample sizes. b. approximately normal if both sample sizes are large. c. exactly normal for any sample sizes. d. exactly normal only if both sample sizes are large. ANS: C PTS: 1 REF: SECTION 9.3 137. If two random samples of sizes n 1 and n 2 are selected independently from two populations with means μ 1 and 2 , then the mean of X 1 - X 2 equals: a. 1 + 2 b. 1 - 2 c. 1 / 2 d. 1 2 ANS: B PTS: 1 REF: SECTION 9.3 138. If two random samples of sizes n 1 and n 2 are selected independently from two non-normally distributed populations, then the sampling distribution of the sample mean difference, X 1 - X 2 , is a. always non-normal b. always normal c. approximately normal only if n 1 and n 2 are both larger than or equal to 30 d. approximately normal regardless of n 1 and n 2 ANS: C PTS: 1 REF: SECTION 9.3 139. If two random samples of sizes n 1 and n 2 are selected independently from two populations with variances σ 1 2 and 2 2 , then the standard error of the sampling distribution of the sample mean difference, X 1 - X 2 , equals: a. ( 1 2 - 2 2 ) / n 1 n 2 b. 1 2 n 1 - 2 2 n 2 c. 1 2 n 1 - 2 2 n 2 d. 1 2 n 1 + 2 2 n 2 ANS: D PTS: 1 REF: SECTION 9.3
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2 140. The standard deviation of X 1 - X 2 is also called the: a. standard error of the difference between two sample means. b.
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This note was uploaded on 09/28/2010 for the course FINOPMGT 250 taught by Professor Kumar during the Spring '10 term at University of Massachusetts Boston.

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SME_8e_Ch_09_Section_3 - CHAPTER 9 SECTION 3: SAMPLING...

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