Econ & Stats Exam: Mean, Variance, Normal Dist., Confidence Intervals, Hypothesis Testing , Exams of Economic statistics

Download Econ & Stats Exam: Mean, Variance, Normal Dist., Confidence Intervals, Hypothesis Testing and more Exams Economic statistics in PDF only on Docsity! Economics 321 Exam 3 December 6, 1991 1 . Use the following information to answer the next 2 questions: The amounts of money spent by six customers at the Havitall Hardware Store were $3.47, 2.21, 7.59, 47.29, 4.32, 26.92, 1.89. What is the sample mean, x. a. $2.99 b. $13.38 c. $27.39 d. $4.32 e. $47.29 2. What is the sample variance s2 a. 16.06 b. 257.69 c. 12.39 d. 423.64 e. 2.01 Use the following information to answer the next 3 ques- tions: Let W, X, an Y be independent normal random variables with parameters n\y = 7,f*X — 27, /iy = 15, and •2W + X - 3Y. = 9,<r2x = .,cr = 10. Consider Z = 3. What is the distribution, of the variable Z a. Normal b. F c. Students t d. X 2 e. None of the above 4. The mean of Z is a. 0 b. 4 c. -4 d. 14 e. 12.4 5. The variance of Z is a. 132 b. 11.49 c. 12 d. 17 e. 22.5 6. What is P(Z > 7) a. 0.957 b. 0.655 c. 0.832 d. 0.168 e. 0.256 Use the following information to answer the next 3 ques- tions: Past records indicate that the daily sales of Pen- ton 35 millimeter cameras at the Camera Corner have a mean of 2.6 and a standard deviation of 1.7 of these 35 milimeter cameras per day. Connie, the manager of Camera Corner, wishes to place an order for Pentons and wants to order enough for the next 40 working days. 7. Find the probability that the mean daily sales during this period X will be at most 3.0 a. 0.01 b. 0.32 c. 0.68 d. 0.07 e. 0.93 8. How many Penton Cameras should Connie or- der to be 0.95 sure of having enough cameras in stock. a. 122 b. 4 c. 3.2 d. 36 e. 1302 Use the following in the next 3 questions: A random sample of size 7 was taken from the normal distribu- tion having an unknown variance <r 2 .(1.7,3.2,-5,-3.3,2.9,- 0.2,2.2). You will need to make use of the fact that / _i\~2 i 5« has a known distribution. V 9. What is the sample variance a. 22.34