Psych60_Midterm1_VersionA_Key

Psych60_Midterm1_VersionA_Key - Psychology 60 Spring, 2011...

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Unformatted text preview: Psychology 60 Spring, 2011 Midterm1 Given 4/18/11 1 PSYCHOLOGY 60 SPRING, 2011 MIDTERM 1 Monday, April 18th, 2011 FULL NAME ___________________________________________________________________________________ STUDENT ID __________________________________________________________________________________ Please put your name and ID number on this page AND on the multiple choice form. VERSION A Psychology 60 Spring, 2011 Midterm1 Given 4/18/11 1) 2 2) If it is not possible to divide the existing categories of a variable, then it is an example of a _________ variable. a. construct b. independent c. dependent d. continuous e. discrete* One item on a questionnaire asks, "How many siblings (brothers and sisters) do you have?" A researcher computes the mean, the median, and the mode for a set of n = 50 responses to this question. Which of the following statements accurately describes the measures of central tendency? a. because the scores are all whole numbers, the mean will be a whole number b. because the scores are all whole numbers, the median will be a whole number c. because the scores are all whole numbers, the mode will be a whole number* d. because the scores are all whole numbers, the mean and median will have the same value e. all of the above are correct descriptions What is the rationale behind using n-1 in calculating the sample standard deviation instead of just N? a. None, you can use either equation interchangeably b. n-1 removes any potential outliers in the sample which could exaggerate the variance c. n-1 will yield a larger result, which is a better reflection of the standard deviation of the population* d. n-1 yields a smaller result, which is a better reflection of the standard deviation of the population e. Both b and d The value of one score in a distribution is changed from X = 20 to X = 30. Which measure(s) of central tendency is (are) certain to change? a. the mean* b. the median c. the mean and the median d. the mode e. cannot determine from the information given Which of the following students scored highest on his/her quiz relative to the other students in his/her class? (Each of the five students took quizzes in different classes.) a. Allen: Score = 65. Quiz mean = 80. Z-score = -5. b. Barbara: Score = 42. Quiz mean = 36. Z-score = +2. c. Chris: Score = 98. Quiz mean = 81. Z-score = +1. d. Davina: Score = 64. Quiz mean = 65. Z-score = -1. e. Enrique: Score = 56. Quiz mean = 40. Z-score = +4.* 3) 4) 5) Psychology 60 Spring, 2011 Midterm1 Given 4/18/11 6) 3 7) A student wants to know the proportion of students who scored above him on the Psych 60 final exam. Assume the scores on this exam are normally distributed. Which of the following information does this student NOT need: a. the number of students in the class** b. the mean of the class c. the standard deviation of the class d. the student's own score e. All the above information is necessary Max is trying to estimate the number of hours the average UCSD student has spent at Disneyland. He collects data from a small sample of eight students, which by random chance happens to include one student whose parents both worked at Disneyland his whole life. His data is as follows (in hours): 4, 19, 0, 52, 19, 36, 2, 11231. Based on these data, which of the following measures of central tendency would not be a good estimate of central tendency? a. Mean* b. Median c. Mode d. A measure of central tendency from a much larger sample. e. The mean, median, and mode of all UCSD students 8) If every score in a population with = 60 and = 8 is transformed into z-scores, then the resulting distribution of z-scores will have a mean of ____ and a standard deviation of ____. a. 0 and 1* b. 60 and 1 c. 0 and 8 d. 60 and 8 (unchanged) e. cannot determine from the information given 9) A population of scores has = 44. In this population, a score of X = 40 corresponds to z = -1.00. What is the population standard deviation? a. 2 b. 4* c. -2 d. -4 e. cannot determine from the information given 10) On an exam with a mean of = 70, you have a score of X = 75. Which of the following values for the standard deviation would give you the highest position within the class? a. = 1* b. = 5 c. = 10 d. = 70 e. cannot determine from the information given Psychology 60 Spring, 2011 Midterm1 Given 4/18/11 4 11) Twenty-five patients are taking a test to determine if they have a particular cognitive disorder. One definition for having this disorder is scoring below 90% of the population on a particular cognitive task. It is known that the population mean score for this task is 50, with a standard deviation of 5. In the sample of 25, the mean score on the task is 45 with a standard deviation of 4. In the population, performance on this task is normally distributed. The doctor is trying to determine at what score he should diagnose patients with this disorder. Help him by determining approximately what score should be used for the diagnosis. a. 43.5 * b. 38.5 c. 45 d. 40 e. cannot determine from the information given 12) Under what circumstances would a score that is 15 points above the mean be considered an extreme score? a. when the population mean is much larger than 15 b. when the population standard deviation is much larger than 15 c. when the population mean is much smaller than 15 d. when the population consists of many more than 15 scores e. when the population standard deviation is much smaller than 15* 13) Unlike the mean, the median: a. is a statistic only used when the data are interval/ratio scale b. is a statistic only used when the data are ordinal c. is highly insensitive to outliers* d. is highly sensitive to outliers e. Both b and c 14) Jon drives to work each morning and the trip takes an average of = 38 minutes. The distribution of driving times is approximately normal with a standard deviation of = 5 minutes. For a randomly selected morning, what is the probability that Jon's drive to work will take between 36 and 40 minutes? a. 0.3446 b. 0.3892 c. 0.1554 d. 0.6554 e. 0.3108* 15) Which set of scores has the smallest standard deviation? a. 11, 17, 31, 53, 64, 18, 23, 19 b. 5, 11, 42, 22 c. 145, 143, 145, 147* d. 27, 105 e. Depends on whether the scores represent a sample or a population Psychology 60 Spring, 2011 Midterm1 Given 4/18/11 5 16) You are investigating how good UCSD students are at spelling by looking at a sample of 10 students. Your measure is how many words are correctly spelled before the student makes a mistake. Some students misspell the very first word, while the majority spell between 5 and 10 words correctly before making a mistake. One student, however, who was a former National Spelling Bee contestant, spells 89 words correctly without making a mistake. Which of the following is true of this data set? a. It is negatively skewed and the mean is greater than the median. b. It is positively skewed and the mean is greater than the median. * c. It is negatively skewed and the mean is lower than the median. d. It is positively skewed and the mean is lower than the median. e. Based on this information, it is impossible to tell the skew and whether the mean or the median is higher. 17) A recent study reports that increased lighting during the winter months results in lower depression scores. For this study, what is the dependent variable? a. the amount of light b. the season of the year c. the level of depression* d. the individuals who participated in the study e. there is no dependent measure in this type of study 18) What is the value of SS for the following sample? Scores: 1, 3, 5 a. SS = 8* b. SS = 8/2 c. SS = 8/3 d. SS = (8)2 e. SS = (8/2)2 19) A researcher investigating how stubbing one's toe causes anger chooses to measure the anger his subjects express as the number of times they swear after stubbing their toes. This researcher's choice to measure "anger" this way is his: a. construct definition b. measurement definition c. discrete definition d. operational definition* e. scale definition 20) For the following distribution, how many people had a score between 40 and 50? a. 10 X f b. 14 60-74 2 c. 12 45-59 14 d. 7 30-44 10 e. cannot determine from the information given* 15-29 7 Psychology 60 Spring, 2011 Midterm1 Given 4/18/11 21) What additional information is obtained by measuring on an interval scale compared to an ordinal scale? a. whether the measurements are the same or different b. the direction of the differences c. the size of the differences* d. Whether the scale has a true zero point e. None of the above 22) What value will you obtain if you add all the deviation scores for a dataset, and then divide that sum by the number of scores in the dataset? a. the sample variance b. the population variance c. you will always get one d. you will always get zero* e. depends on whether the data are being used as a population of a sample 6 Make sure you bubbled in correctly which Test Form you were taking. We cannot score your exam without this! Before continuing, check that you have done this. Psychology 60 Spring, 2011 Midterm1 Given 4/18/11 7 Short Answer / Computation Questions: VERSION A For these questions, you must show your work in order to receive credit (do not simply write your final answer) but only your final answer will be graded. If you are using a formula to solve the question, write the formula first, and then apply the formula to the problem. Write legibly and put your FINAL ANSWER in the BOX for each question 23) A market researcher interested in how much individuals on the UCSD campus talk on their phones takes a sample of 6 students and asks them to report how many minutes a day they talk on their phone. The following are the data this researcher obtains: 39, 81, 59, 4, 18, 27 a. Find the value of SS for this sample. b. Xbar = 228/6 = 38 X 39 81 59 4 18 27 X-Xbar 1 43 21 -34 -20 -11 (X-Xbar)2 1 1849 441 1156 400 121 X 39 81 59 4 18 27 = 228 X2 1521 6561 3481 16 324 729 = 12632 (X-Xbar)2 = 3968 Or !X 2 i ( !X i ) " n 2 , 12632 2282/6 = 3968 Final Answer: 3968 c. Assume that SS = 4000 (DO NOT USE ANY OTHER VALUE FOR SS). Find the estimate of the standard deviation of the population. SS Estimate of ! = s = n !1 s= 4000 5 s = 800 s = 28.28 Final Answer: 28.28 Psychology 60 Spring, 2011 Midterm1 Given 4/18/11 8 24) A researcher interested in sleep collected a sample of 10 individuals and recorded how long each of them slept for a single night. She correctly calculated the sample mean to be X = 8 , but accidently used the population formula to calculate the standard deviation. The value she found for the standard deviation with this incorrect formula was 3. Determine the correct value; that is, find the value that she should use to estimate the population standard deviation from this sample. SS != N 3= s= SS SS !9= " SS = 90 10 10 SS 90 !s= ! s = 10 n #1 9 s = 3.16 25) A research firm is interested in obtaining a sample of individuals who use Facebook a "typical amount of time per day," which they specifically define as the middle 34% of people in terms of hours spent per day on the website. Assume that Facebook usage, in terms of hours per day, is normally distributed with = 4.2, and = 1. Determine the values in number of hours per day that this research firm should use in recruiting subjects (note: your answer will have two values, a lower value and an upper value, that defines the "typical amount of time per day" region as stated above). p( -0.44 < Z < 0.44 ) = .34 i i Xlower = 4.2 + (-0.44)(1) = 3.76 hours Xupper = 4.2 + (+0.44)(1) = 4.64 hours Final Answer: s = 3.16 X = + z! Final Answer: 3.76 hours to 4.64 hours Psychology 60 Spring, 2011 Midterm1 Given 4/18/11 9 Psychology 60 Spring, 2011 Midterm1 Given 4/18/11 10 ...
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This note was uploaded on 01/10/2012 for the course PSYC PSYC 60 taught by Professor ? during the Winter '09 term at UCSD.

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