Psychologist use statistics for 2 things

O Summarize the information from the study/experimentO Measures of

central tendencyO MeanO MedianO Mode

O Make judgements and decisions about the dataO See if groups

differ from each other

O See if two variables are related to each other

Measures of Variation

O RangeO Difference b/t

the highest score and the lowest scoreO extreme scores

can also create a deceptive range

O Standard DeviationO Measure of how

much scores vary around the mean scoreO Are scores

packed together or dispersed?

Standard DeviationTest Scores in Class A Test Scores in Class BScore Deviatio

n from the Mean

Squared Deviation

Score Deviation from the Mean

Squared Deviation

72 -8 64 60 -20 40074 -6 36 60 -20 40077 -3 9 70 -10 10079 -1 1 70 -10 10082 +2 4 90 +10 10084 +4 16 90 +10 10085 +5 25 100 +20 40087 +7 49 100 +20 400

204 2000640 640Sum of all scores Mean=640÷8=80

Standard Deviation

O Class A Class BO

O So, what does this tell us about each class’s score on the test?O Remember the mean is 80.

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 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.

How do we know whether an observed difference can be generalized to other

populations?O Inferential statistics

O Representative samples are better than biased samples.

O Less-variable observations are more reliable than those that are more variable.

O 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 t-testO F-test or analysis of varianceO chi-square

Inferential StatisticsStatistical 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.

Practice Questions1. Descriptive statistics ______, while

inferential statistics _______.a. indicate the significance of the data;

summarize the datab. describe data from experiments; describe

data from surveys and case studiesc. are measures of central tendency; are

measures of variance.d. determine if data can be generalized to

other populations; summarize datae. summarize data; determine if data can be

generalized to other populations

Practice Questions2. 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%

Practice Questions3. When a distribution of scores is

skewed, which of the following is the most representative measure of central tendency?

a. Inferenceb. Standard deviationc. Meand. Mediane. Correlation coefficient

IQ Mini-LessonO What is intelligence?

IntelligenceThe 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.

Intelligence WarsO Intelligence: mental quality consisting

of the ability to learn from experience, solve problems, and use knowledge to adapt to new situationsO Socially constructed by a cultureO Usually referred to as “school smarts”

O Several intelligence theoriesO Do we have an inborn mental capacity?O Can it be quantified with a number?

Intelligence WarsO Spearman’s General Intelligence or gO Gardner’s Multiple IntelligencesO Sternberg’s Triarchic Theory of

Intelligence

Create a trifold foldable that compares and contrasts historic and contemporary theories of intelligence

Assessing IntelligenceO Intelligence is whatever intelligence

tests measureO Intelligence test—a method for

assessing an individual's mental aptitudes and comparing them with those of others, using numerical scores

Assessing Intelligence (not in your book)

O Francis GaltonO Eugenics— “well-born”; the practice

of encouraging supposedly superior people to reproduce, while discouraging or even preventing those judged inferior from doing so

Assessing IntelligenceO Alfred BinetO Lewis TermanO David Wechsler

O Create a trifold foldable to identify key contributors in intelligence research and testing, and list characteristics of how psychologist measure intelligence

Modern TestsO Aptitude tests—designed to predict

a person’s future performance as aptitude is the capacity to learnO ACT (American College Test) seeks to

predict your ability to do well in college

O Achievement tests—designed to assess what a person has learnedO EOC (End of Course exam) seeks to

assess what you learned in the course

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 testO Tests need to be constantly restandardized

to properly assess different generations—Flynn Effect (intelligence scores have been rising over time)

Principles to Test Construction:

StandardizationO 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.

Principles of Test Construction:Reliability

O The extent to which a test yields consistent resultsO Measured by 2 test halves, alternate

forms, or retestingO 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

Principles of Test Construction:Validity

O The extent to which a test measures or predicts what it is supposed toO Content validity—the extent to which a test

samples the behavior that is of interestO A driving test assess driving tasks

O Predictive validity—the success with which a test predicts the behavior it is designed to predictO Criterion—the behavior a test is designed to

predictO ACT is designed to predict future college

performance with is the criterion

Practice QuestionsO Which type of correlation would show

the best reliability in a test-retest situation?

Practice Questions1. 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 testingb. Validationc. Content validationd. Standardizatione. Predictive validity

Practice Questions1. 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 testse. Gradual improvement in intelligence test

scores over the last several decades

Practice Questions1. 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 validity2. Split-half reliability3. Content validity4. Test-retest reliability5. Standard validity