rubric+stats

AP ® PSYCHOLOGY 2003 SCORING GUIDELINES Copyright © 2003 by College Entrance Examination Board. All rights reserved. Available at apcentral.collegeboard.com. 2 Question 1 General Principles 1. No circular definitions (e.g., can’t use the concepts to define themselves). 2. Points generally will not be awarded when an answer directly contradicts correct information with incorrect information. 3. Answers must be presented in sentences, and sentences must be cogent enough for the student’s meaning to come through. Graphs by themselves are not sufficient, but annotated graphs can constitute “descriptions” or “definitions.” 4. Spelling and grammar mistakes do not reduce a student’s score, but spelling must be close enough so that the reader is convinced of the word in question. Mistakes in word choice are not forgiven, even if the context suggests the student wrote the wrong word by accident. 5. Assume that the student is working with a frequency distribution with scores ordered. A. Statistics are often used to describe and interpret the results of intelligence testing. Describe three measures of central tendency (mean, median, and mode) Point 1 : Mean • the average score • the sum of the scores divided by the (total) number of scores ( Σ X / N) Point 2 : Median • the middle score • score that divides distribution in half Point 3 : Mode • the most frequent score • score that shows up more than others Point 4: Describe a skewed distribution • An asymmetrical distribution of scores Examples: “curve with a bump on the left and tail to the right” “most scores are bunched to the left (or right) of the mean” • long tail in one direction • the mean is not the same as the median (or mode) • extreme scores pull the mean NOTES: a) Any description or example of a skewed distribution is OK. b) Don’t confuse with point #6. TRAP: Do not score “not normal.” (Distributions that are not normal can be symmetrical.) Point 5 : Relate the three measures of central tendency to a normal distribution • Mean, median, and mode are the same (“very close,” “very similar”) median NOTES: a) Must mention all three measures (or say “all measures”) mode b) Description of normal distribution by itself is not sufficient Pt #7: 55 70 85 100 115 130 145    AP ® PSYCHOLOGY 2003 SCORING GUIDELINES Copyright © 2003 by College Entrance Examination Board. All rights reserved. Available at apcentral.collegeboard.com. 3 Question 1 (cont’d.) Point 6: Relate the three measures of central tendency to a positively skewed distribution • The mean is the largest • The mode or the median are smaller than the mean • The mean is a less useful measure • The median is more useful NOTES: a) Must compare, at least implicitly, the measures of central tendency b) Assume statements about a measure are referring to its value (magnitude), not frequency. Point 7: An intelligence test for which the scores are normally distributed has a mean of 100 and a standard deviation of 15. Use this information to describe how the scores are distributed. • Most scores (or 60-75%) are within 15 points of the mean (of 100) • The typical (average, normal) IQ score falls between 85 and 115 NOTES: a) Answer must properly apply standard deviation of 15 points in computing range around mean ± 2 s.d. = 70 and 130; ± 3 s.d. = 55 and 145 (see normal curve figure) TRAP: “In this distribution, the scores range from 85 to 115” does not score. (Only 68% of scores are within 85 to 115, not the entire range of scores.) Point 8: In two normal distributions, the means are 100 for group I and 115 for group II. Can an individual in group I have a higher score than the mean score for group II? Explain.  • Answer must recognize that not all scores in a distribution are at the mean o There can be an overlap between the groups because someone can have a score above the mean o The mean is only an average, some people score above and some below NOTE: It is possible for a score from Group I to be higher than some scores in Group II, but it is not necessary. Answer can describe non-overlapping distributions. TRAP: “standard deviation” by itself is not sufficient, but a complete example using the concept of a standard deviation is acceptable (e.g., “Depending upon the size of the s.d., scores larger than 115 are possible.”) B. Apply knowledge of psychological research in answering the following questions about intelligence scores. Point 9: Explain why norms for standardized intelligence tests are periodically updated. • Changes in knowledge require tests to be re-normed. Examples (not exhaustive): o People have gotten smarter (Flynn effect) o The number of questions answered accurately has increased over the years. o Changes that affect IQ test scores of groups (e.g., socio-cultural or technological) o Changes in educational practices or techniques (that affect knowledge) o Keep material culturally relevant, remove references to obsolete issues • Re-norm to maintain validity or reliability TRAP: changes in social norm s alone (as opposed to test norms) are not reasons that test norms are updated (two different uses of the word “norm”)    