Psychologist use statistics for 2 things

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Caroline Nicholson
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1 Psychologist use statistics for 2 things O Summarize the information from the study/experiment O Measures of central tendency O Mean O Median O Mode O Make judgements and decisions about the data O See if groups differ from each other O See if two variables are related to each other

2 Measures of Variation O Range O Difference b/t the highest score and the lowest score O extreme scores can also create a deceptive range O Standard Deviation O Measure of how much scores vary around the mean score O Are scores packed together or dispersed?

3 Sum of all scores Test Scores in Class A Score Standard Deviation Deviation from the Mean Squared Deviation Test Scores in Class B Score Deviation from the Mean Squared Deviation Mean=640 8=80

4 Standard Deviation O Standard Deviation = O Class A sum of (deviations)2 Number of scores Class B O 204 = = 15.8 O So, what does this tell us about each class s score on the test? O Remember the mean is 80.

5 Well, what s all this look like on a graph.

Inferential Statistics: Involves estimating what is happening in a sample population for the purpose of making decisions about that population s

Basically, inferential stats allow us to say: If it worked for this population, we can estimate it will work for the rest of the population.

6 Inferential Statistics: Involves estimating what is happening in a sample population for the purpose of making decisions about that population s characteristics (based in probability theory). Basically, inferential stats allow us to say: If it worked for this population, we can estimate it will work for the rest of the population. ie - Drug Testing -- if the meds worked for the sample, we estimate they will have the same effect on the rest of the population. There is always a chance for error in whatever the findings may be, so the hypothesis & results must be tested for significance.

7 How do we know whether an observed difference can be generalized to other populations? O Inferential statistics O O O Representative samples are better than biased samples. Less-variable observations are more reliable than those that are more variable. More cases are better than fewer. O Statistical significance: indicates the likelihood that a result will happen by chance (psychologists like 5% left to chance) O O O t-test F-test or analysis of variance chi-square

Data is significant when the likelihood of a difference being due to chance is less than 5 times out of 100. In other words.

8 Inferential Statistics Statistical Significance - difference observed between 2 groups is probably NOT due to chance. The difference instead is likely due to a real difference between the samples. Data is significant when the likelihood of a difference being due to chance is less than 5 times out of 100. In other words... There is a 95% chance (or greater) likelihood that any difference seen is due to your independent variable shown numerically as p <.05 Important because if research is statistically significant it means that the results are probably not a fluke or due to chance.

9 Practice Questions 1. Descriptive statistics, while inferential statistics. a. indicate the significance of the data; summarize the data b. describe data from experiments; describe data from surveys and case studies c. are measures of central tendency; are measures of variance. d. determine if data can be generalized to other populations; summarize data e. summarize data; determine if data can be generalized to other populations

10 Practice Questions 2. In a normal distribution, what percentage of the scores in the distribution falls within one standard deviation on either side of the mean? a. 34% b. 40% c. 50% d. 68% e. 95%

11 Practice Questions 3. When a distribution of scores is skewed, which of the following is the most representative measure of central tendency? a. Inference b. Standard deviation c. Mean d. Median e. Correlation coefficient

12 IQ Mini-Lesson O What is intelligence?

13 Intelligence The ability to learn from experience, solve problems, and use knowledge to adapt to new situations. Is socially constructed thus Can be culturally specific. According to this definition, are both Einstein and Ruth intelligent? Human beings are uniquely intelligent, and the form of that intelligence is unique in all of us.

14 Intelligence Wars O Intelligence: mental quality consisting of the ability to learn from experience, solve problems, and use knowledge to adapt to new situations O Socially constructed by a culture O Usually referred to as school smarts O Several intelligence theories O Do we have an inborn mental capacity? O Can it be quantified with a number?

15 Intelligence Wars O Spearman s General Intelligence or g O Gardner s Multiple Intelligences O Sternberg s Triarchic Theory of Intelligence Create a trifold foldable that compares and contrasts historic and contemporary theories of intelligence

16 Assessing Intelligence O Intelligence is whatever intelligence tests measure O Intelligence test a method for assessing an individual's mental aptitudes and comparing them with those of others, using numerical scores

17 Assessing Intelligence (not in your book) O Francis Galton O Eugenics well-born ; the practice of encouraging supposedly superior people to reproduce, while discouraging or even preventing those judged inferior from doing so

18 Assessing Intelligence O Alfred Binet O Lewis Terman O David Wechsler O Create a trifold foldable to identify key contributors in intelligence research and testing, and list characteristics of how psychologist measure intelligence

19 Modern Tests O Aptitude tests designed to predict a person s future performance as aptitude is the capacity to learn O ACT (American College Test) seeks to predict your ability to do well in college O Achievement tests designed to assess what a person has learned O EOC (End of Course exam) seeks to assess what you learned in the course

20 Principles to Test Construction: Standardization O Standardization defining meaningful scores by comparison with the performance of a pretested standardization group, while also using uniform instructions for administration of test O Tests need to be constantly restandardized to properly assess different generations Flynn Effect (intelligence scores have been rising over time)

O Principles to Test Construction: Standardization When a test is standardized, the results when graphed typically form a normal curve symmetrical bell-shaped curve that describes the

21 O Principles to Test Construction: Standardization When a test is standardized, the results when graphed typically form a normal curve symmetrical bell-shaped curve that describes the distribution of many physical and psychological attributes; most scores fall near the average and fewer and fewer scores lie near the extreme O On an intelligence test, the average score is 100.

22 Principles of Test Construction: Reliability O The extent to which a test yields consistent results O Measured by 2 test halves, alternate forms, or retesting O Internal consistency similar questions about the same learning goal to measure if similar constructs assess the appropriate goal O People should generally score the same when the test is taken multiple times

23 Principles of Test Construction: Validity O The extent to which a test measures or predicts what it is supposed to O Content validity the extent to which a test samples the behavior that is of interest O A driving test assess driving tasks O Predictive validity the success with which a test predicts the behavior it is designed to predict O Criterion the behavior a test is designed to predict O ACT is designed to predict future college performance with is the criterion

24 Practice Questions O Which type of correlation would show the best reliability in a test-retest situation?

25 Practice Questions 1. A test developer defines uniform testing procedures and meaningful scores by comparison with the performance of a pretested group. Which of the following best describes this process? a. Reliability testing b. Validation c. Content validation d. Standardization e. Predictive validity

26 Practice Questions 1. The Flynn effect refers to the a. Superiority of certain racial and ethnic groups on intelligence tests b. Extreme scores (very high and very low) that are more common for males than females on math tests c. Stereotype threat that may cause some African- American students to underperform on standardized tests d. Predictive ability of intelligence tests e. Gradual improvement in intelligence test scores over the last several decades

27 Practice Questions 1. Students who do well on college entrance exams generally do well in their first year of college. This helps establish that these exams have 1. Predictive validity 2. Split-half reliability 3. Content validity 4. Test-retest reliability 5. Standard validity

Testing and Individual Differences

Testing and Individual Differences College Board Objectives: AP students in psychology should be able to do the following: Define intelligence and list characteristics of how psychologists measure intelligence: