Microsoft Word - MIDTERM09.doc Standard Normal Cumulative Probability Table Midterm Examination Communication 800, 2020 Name Instructions: Answer each question in the space provided. If you need more...

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Microsoft Word - MIDTERM09.doc Standard Normal Cumulative Probability Table Midterm Examination Communication 800, 2020 Name Instructions: Answer each question in the space provided. If you need more space, use a separate sheet of paper and attach to show all of your work. Part 1. Short Answer. 1. Find the median, mean and standard deviation for the following four scores: a. -1, 0, +1, +1. Show all calculations. (4) 2. What can you conclude if the mean exceeds the median in a distribution of scores? (1) 3. What can you conclude if the median exceeds the mode in a distribution of scores? (1) 1 4. Suppose Z is normally distributed with a mean of 0 and standard deviation of 1. Using the tables that are appended, find the proportion of cases such that… (each worth 3 points) (a) Z is greater than .60. (b) Z is less than –.70. (c) Z is between –1 and –2. (d) Z is between –.5 and 1.5. 5. Suppose that a college estimates the following probability distribution for X = number of courses taken by a full-time student this semester: Value of X 3 4 5 6 Probability 0.07 0.25 0.28 (a)What is the probability of X=4? (4) 7. What is the correlation coefficient for each of the following three data sets? (No calculation should be necessary). (6) (a) x y (b) x y (c) x y 0 2 3 6 0 2 1 4 7 6 1 1 2 6 4 6 2 0 8. You are taking a midterm exam that consists of 10 true-false questions. For each question, there is only one correct answer. (a) Suppose you have not studied for the midterm and randomly guess on each question, with a 50/50 chance of answering any given question correctly. What is the probability that you will get exactly 5 questions right on the midterm? (5) (b) Now, suppose you are reasonably well-prepared for the exam and have answered 80% of questions correctly on various practice tests. What is the probability that you will get at least 9 questions right on the midterm? (5) Part 2. Multiple Choice. Circle the letter next to the answer that best completes each question. (each question is worth 2 points) 10. For a test to be reliable it must capture accurate information. (a) True (b) False 11. A standardized test designed to measure math anxiety has a mean of 100 and a standard deviation of 10. Which of the following scores would you suspect is an outlier. (a) 140 (b) 100 (c) 80 (d) all of the above (e) none of the above 12. The median is often preferable to the mean as a measure of central tendency when (a) the distribution is highly skewed. (b) the sample is large. (c) the variance is large. (d) the variable is measured on an interval scale. 13. A correlation of -.81 between variables x and y indicates that (a) there is a weak relationship between x and y. (b) x causes y. (c) there is a strong relationship between x and y. (d) y causes x. 14. If we can establish that variable X comes before variable Y in time, then we can say with a reasonable degree of confidence that (a) X is a cause of Y. (b) X is not a cause of Y. (c) Y is a cause of X. (d) Y is not a cause of X. (e) Y may cause X. 15. A stratified random sample combines the benefits of (a) a simple random sample and a systematic sample. (b) a simple random sample and a quota sample. (c) a cluster sample and a snowball sample. (d) a random sample and random assignment. 16. If you increase the size of a convenience sample from 50 to 1,000 the accuracy of the sample will increase. (a) quadrupled. (b) doubled. (c) unchanged. (d) unknown. 17. Which of the following is a nominal (categorical) variable? (a) years of education. (b) age. (c) marital status. (d) grade point average. (e) not enough information to know. 18. Compared with an ordinal scale, an interval scale (a) is a lower level of measurement. (b) contains more information. (c) is less desirable. (d) is less biased. 19. Scientists typically study samples rather than populations primarily to (a) increase external validity. (b) eliminate bias. (c) estimate error. (d) reduce cost 20. A random sample of 1200 people is used to estimate the unemployment rate in New York City (pop. 8 million). How large a sample would be needed to estimate the unemployment rate in the entire U.S. (pop. 250 million) with roughly the same degree of accuracy? (Assume that the unemployment rate is about the same in the two populations). (a) about 28 times larger. (b) about √(28) times larger. (c) same size. (d) can’t tell from the information given Cumulative probabilities for NEGATIVE z-values are shown in the following table: z 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 -3.4 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0003 0.0002 -3.3 0.0005 0.0005 0.0005 0.0004 0.0004 0.0004 0.0004 0.0004 0.0004 0.0003 -3.2 0.0007 0.0007 0.0006 0.0006 0.0006 0.0006 0.0006 0.0005 0.0005 0.0005 -3.1 0.0010 0.0009 0.0009 0.0009 0.0008 0.0008 0.0008 0.0008 0.0007 0.0007 -3.0 0.0013 0.0013 0.0013 0.0012 0.0012 0.0011 0.0011 0.0011 0.0010 0.0010 -2.9 0.0019 0.0018 0.0018 0.0017 0.0016 0.0016 0.0015 0.0015 0.0014 0.0014 -2.8 0.0026 0.0025 0.0024 0.0023 0.0023 0.0022 0.0021 0.0021 0.0020 0.0019 -2.7 0.0035 0.0034 0.0033 0.0032 0.0031 0.0030 0.0029 0.0028 0.0027 0.0026 -2.6 0.0047 0.0045 0.0044 0.0043 0.0041 0.0040 0.0039 0.0038 0.0037 0.0036 -2.5 0.0062 0.0060 0.0059 0.0057 0.0055 0.0054 0.0052 0.0051 0.0049 0.0048 -2.4 0.0082 0.0080 0.0078 0.0075 0.0073 0.0071 0.0069 0.0068 0.0066 0.0064 -2.3 0.0107 0.0104 0.0102 0.0099 0.0096 0.0094 0.0091 0.0089 0.0087 0.0084 -2.2 0.0139 0.0136 0.0132 0.0129 0.0125 0.0122 0.0119 0.0116 0.0113 0.0110 -2.1 0.0179 0.0174 0.0170 0.0166 0.0162 0.0158 0.0154 0.0150 0.0146 0.0143 -2.0 0.0228 0.0222 0.0217 0.0212 0.0207 0.0202 0.0197 0.0192 0.0188 0.0183 -1.9 0.0287 0.0281 0.0274 0.0268 0.0262 0.0256 0.0250 0.0244 0.0239 0.0233 -1.8 0.0359 0.0351 0.0344 0.0336 0.0329 0.0322 0.0314 0.0307 0.0301 0.0294 -1.7 0.0446 0.0436 0.0427 0.0418 0.0409 0.0401 0.0392 0.0384 0.0375 0.0367 -1.6 0.0548 0.0537 0.0526 0.0516 0.0505 0.0495 0.0485 0.0475 0.0465 0.0455 -1.5 0.0668 0.0655 0.0643 0.0630 0.0618 0.0606 0.0594 0.0582 0.0571 0.0559 -1.4 0.0808 0.0793 0.0778 0.0764 0.0749 0.0735 0.0721 0.0708 0.0694 0.0681 -1.3 0.0968 0.0951 0.0934 0.0918 0.0901 0.0885 0.0869 0.0853 0.0838 0.0823 -1.2 0.1151 0.1131 0.1112 0.1093 0.1075 0.1056 0.1038 0.1020 0.1003 0.0985 -1.1 0.1357 0.1335 0.1314 0.1292 0.1271 0.1251 0.1230 0.1210 0.1190 0.1170 -1.0 0.1587 0.1562 0.1539 0.1515 0.1492 0.1469 0.1446 0.1423 0.1401 0.1379 -0.9 0.1841 0.1814 0.1788 0.1762 0.1736 0.1711 0.1685 0.1660 0.1635 0.1611 -0.8 0.2119 0.2090 0.2061 0.2033 0.2005 0.1977 0.1949 0.1922 0.1894 0.1867 -0.7 0.2420 0.2389 0.2358 0.2327 0.2296 0.2266 0.2236 0.2206 0.2177 0.2148 -0.6 0.2743 0.2709 0.2676 0.2643 0.2611 0.2578 0.2546 0.2514 0.2483 0.2451 -0.5 0.3085 0.3050 0.3015 0.2981 0.2946 0.2912 0.2877 0.2843 0.2810 0.2776 -0.4 0.3446 0.3409 0.3372 0.3336 0.3300 0.3264 0.3228 0.3192 0.3156 0.3121 -0.3 0.3821 0.3783 0.3745 0.3707 0.3669 0.3632 0.3594 0.3557 0.3520 0.3483 -0.2 0.4207 0.4168 0.4129 0.4090 0.4052 0.4013 0.3974 0.3936 0.3897 0.3859 -0.1 0.4602 0.4562 0.4522 0.4483 0.4443 0.4404 0.4364 0.4325 0.4286 0.4247 0.0 0.5000 0.4960 0.4920 0.4880 0.4840 0.4801 0.4761 0.4721 0.4681 0.4641 Standard Normal Cumulative Probability Table Cumulative probabilities for POSITIVE z-values are shown in the following table: z 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.0 0.5000 0.5040 0.5080 0.5120 0.5160 0.5199 0.5239 0.5279 0.5319 0.5359 0.1 0.5398 0.5438 0.5478 0.5517 0.5557 0.5596 0.5636 0.5675 0.5714 0.5753 0.2 0.5793 0.5832 0.5871 0.5910 0.5948 0.5987 0.6026 0.6064 0.6103 0.6141 0.3 0.6179 0.6217 0.6255 0.6293 0.6331 0.6368 0.6406 0.6443 0.6480 0.6517 0.4 0.6554 0.6591 0.6628 0.6664 0.6700 0.6736 0.6772 0.6808 0.6844 0.6879 0.5 0.6915 0