
In Problem 14 in Chapter 11, we described a study Showing that students are likely to improve their test
Scores if they go back and change answers after reconsidering some of the questions on the exam (Johnston, 1975). In the study, one group of students was encouraged to reconsider each question and
to change answer whenever they felt it was appropriate ate. The students were asked to record their original answers as well as the changes. For each student, the exam was graded based on the original answers and on the changed answers. For a group of n = 40 students
oppose that 26 had higher scores for the changed answer version and only 14 had higher scores for
the original-answer version. Is this result significantly
different from chance? Use a two-tailed test with a = .01.
There is some evidence suggesting that you are likely to improve your test score if you rethink and change answers on a multiple-choice ex am, (Johnston, 1975). To determine this phenomenon a teacher gave the same final exam to two section of a psychology course. The students in one section were told to tum in their exams immediately after finishing, without changing any of their answer. In the other section, students were encouraged to reconsider each question and to change answers whenever they felt it was appropriate. Before the final exam, the teacher had matched 9 students in the first section with 9 students in the second section based on their midterm grades. For example, a student in the no-change section with an 89 on the midterm exam was matched with student in the change section who also had an 89 on the midterm. The difference between the two final exam grades for each matched pair was computed and the data showed that the students who were allowed to change answers scoring higher by an average of MD = 7 point With SS = 288.
- Do the data indicate a significant difference between the two conditions? Use a two-tailed test with a = .05.
- Construct a 95% confidence
interval to estimate the size of the population mean difference.

Want to see the full answer?
Check out a sample textbook solution
Chapter 18 Solutions
Statistics for The Behavioral Sciences (MindTap Course List)
- At the same restaurant as in Question 19 with the same normal distribution, what's the chance of it taking no more than 15 minutes to get service?arrow_forwardClint, obviously not in college, sleeps an average of 8 hours per night with a standard deviation of 15 minutes. What's the chance of him sleeping between 7.5 and 8.5 hours on any given night? 0-(7-0) 200 91109s and doiw $20 (8-0) mol 8520 slang $199 galbrog seam side pide & D (newid se od poyesvig as PELEO PER AFTE editiw noudab temand van Czarrow_forwardTimes to complete a statistics exam have a normal distribution with a mean of 40 minutes and standard deviation of 6 minutes. Deshawn's time comes in at the 90th percentile. What percentage of the students are still working on their exams when Deshawn leaves?arrow_forward
- Suppose that the weights of cereal boxes have a normal distribution with a mean of 20 ounces and standard deviation of half an ounce. A box that has a standard score of o weighs how much? syed by ilog ni 21arrow_forwardBob scores 80 on both his math exam (which has a mean of 70 and standard deviation of 10) and his English exam (which has a mean of 85 and standard deviation of 5). Find and interpret Bob's Z-scores on both exams to let him know which exam (if either) he did bet- ter on. Don't, however, let his parents know; let them think he's just as good at both subjects. algas 70) sering digarrow_forwardSue's math class exam has a mean of 70 with a standard deviation of 5. Her standard score is-2. What's her original exam score?arrow_forward
- Clint sleeps an average of 8 hours per night with a standard deviation of 15 minutes. What's the chance he will sleep less than 7.5 hours tonight? nut bow visarrow_forwardSuppose that your score on an exam is directly at the mean. What's your standard score?arrow_forwardOne state's annual rainfall has a normal dis- tribution with a mean of 100 inches and standard deviation of 25 inches. Suppose that corn grows best when the annual rainfall is between 100 and 150 inches. What's the chance of achieving this amount of rainfall? wved now of sociarrow_forward
- Holt Mcdougal Larson Pre-algebra: Student Edition...AlgebraISBN:9780547587776Author:HOLT MCDOUGALPublisher:HOLT MCDOUGALGlencoe Algebra 1, Student Edition, 9780079039897...AlgebraISBN:9780079039897Author:CarterPublisher:McGraw Hill

