CHAPTER 1 LECTURE NOTES



CHAPTER 1 Lecture Notes

The Scientific Attitude

Prepares us to think smarter

Scientific approach: skeptical but open-minded, humble

➢ Shifts away from illusions to reality, we must use smart thinking or critical thinking: thinking that does not blindly accept things, but approaches with skepticism and examines the evidence carefully:

How did they know, on guts and instinct? Are the evidence biased?

• remember, extreme humility = stubbornness

• critical thinking: examines assumptions

discerns hidden value

evaluates evidence

assesses conclusions

The Limits of Intuition and Common Sense

❖ Intuition often ends up nowhere

❖ Hindsight bias: tendency to believe that one would have known it after the results are in.

“I knew it all along!”

❖ Humans tend to be overconfident. We think we know more than we actually do (probably result of self-serving bias)

o Hindsight causes us to be overconfident as we believe we would have picked the answer when the results are in front of us.

❖ False Consensus Effect: tendency to overestimate others’ agreement with us. E.g. Vegetarians believe larger % of population is vegetarian than carnivores.

❖ Illusory Correlation: perceiving correlation when non exists. Notice random coincidences as not random. E.g. As soon as couples stop trying to unsuccessfully conceive and adopt a baby, a year or two later, they conceive and have a child together.

The Scientific Method

❖ Scientific theory: explanation using set of principles to organize/predict observations

❖ No matter how good theory sounds, must put it to test

❖ Must imply testable prediction = hypothesis

❖ Beware of bias when testing

❖ Good experiments can be replicated: experiment can be repeated and would yield constant results: done with a different group of people

Types of Research

❖ Case study: research method where one person is studied in depth to find universal principles (things that apply to all)

o Drawback: that the individual being studied could be atypical, results not universally contained

❖ Survey: research method to get the self-reported attitudes/behaviors of people

o Drawback: looks at cases in less depth and wording of questions affects the response given (framing) We tend to hang around group similar to us so using them as study is wrong

❖ Naturalistic Observation: observing and recording behavior in natural settings without any control of the situation

o Like case study & survey, naturalistic observation does not explain behavior

❖ Correlation: the way two factors vary and how well one factor may show a relationship to the other

o positive correlation: direct relationship where factors increase or

decrease together.

▪ Self-esteem grades = Positive correlation

▪ Study time grades = Positive correlation

o Negative correlation: inverse relationship where one factor increases while the other

decreases

▪ Party every night grades OR Alcohol intake self-esteem

CORRELATION DOES NOT PROVE CAUSATION,

IT SIMPLY SHOWS A RELATIONSHIP (+ OR -) BETWEEN TWO FACTORS

Experiments

o To isolate cause & effect … to prove causation

o Population: all the cases in the group being studied (all students at ANA with ADHD not receiving medication)

o Random sampling: sample that gives each member of population a 50-50 chance of being selected .. to ensure results within range

o Random assignment: assigning subjects from random sampling group to experimental or control groups to ensure no bias.

o Experimental condition: condition that exposes subject to treatment (given pill to lessen effects of ADHD)

o Control condition: serves as a static comparison to observe effects of treatment on experimental condition subjects; subjects not exposed to treatment (given placebo pill … no effect on ADHD)

o Independent variable: experimental factor being manipulated and studies (pill that lessens ADHD)

o Dependent variable: factor that depends on manipulation of independent variable (placebo pill)

o Placebo: inert substance/condition that may be administered instead of an actual active agent

o Double blind procedure: procedure in which neither the experimenter nor the subjects know which group is given treatment and which is not

Chapter 1 (addendum): Statistics

➢ Percentile Rank: percentage that describes your rank among those also being evaluated. (If your percentile rank on a test is 90, then your score is higher than 90% of the class.) It is impossible to get 100% percentile rank because you cannot get higher than everyone in the class, including yourself.

➢ Mean: average score ….. add all the numbers up and divide by number of items. (The mean of {2,2,3,10, 98} is 23.)

➢ Median: middle point of all the items such that half is above the number and half is below the number (50th percentile). Arrange numbers from highest to lowest or vice versa and find the number in the middle. (The median of {2,2,3,10, 98} is 3.)

➢ Mode: number that occurs the most. (The mode of {2,2,3,10, 98} is 2)

➢ Range: range of the scores is the difference between the highest number and the lowest number. (The range of a GPA score is from 0.0 to – 4.0

➢ Standard Deviation: measurement of how far scores differ/deviate from the mean (average).

o The standard deviation of {5,6,5,6,6,7,5,4} is very low because all the items barely deviate from the mean of 5.5.

o Whereas, the standard deviation of {5,10,8,18,-6.5,-7.22} is high.

|Find the Standard Deviation of {2,3,3,4} | |

|1.) Find the mean |(2+3+3+4)/4 = 3 |

|2.) Subtract the mean from each term and square it. |(2-3)2 = 1, (3-3) 2 = 0, (3-3) 2 = 0, (4-3)2 = 1 |

|3.) Find the average of the deviations from the mean. |(1+0+0+1)/4 = 0.5 |

|4.) Square root the average and that is the standard deviation | (0.5 = 0.7071 |

| | |

| |Normally, this number would be rounded to the same decimal place |

| |as the data, but 0.7071 is shown for clearer understanding. |

| |(0.7071 = 1) |

➢ Normal curve: (bell curve) a distribution graph that dictates 68% of the scores should circa the mean. More specifically, 68% of the scores should fall within 1 standard deviation and 95% should fall within 2 standard deviations from the mean.

➢ Scatterplot: graphical representation of data by using dots. The degree of cluster or formation of a slope can dictate the correlation between two variables.

➢ Correlation: relationship between 2 events. (Traffic accidents increase with increasing temperatures; business earnings drop as Christmas ends.)

o Correlation Coefficient: A proportional number that measures correlation - how strongly two events vary

▪ Positive Correlation: two events increase and/or decrease together. (increasing study time positively correlates with increasing grades; or decreased food consumption positively correlates with decreased weight.)

• Positive correlation coefficients are positive numbers ranging from 0.00 (no correlation) to 1.00 (perfect correlation). In a scatterplot graph, a positive correlation exists if a positive slope is seen

▪ Negative Correlation: one event increases and the other decreases or vice versa. (decreasing number of hours of sleep negatively correlates with increases in traffic accidents; or increasing alcohol consumption decreases alertness.) negative correlation coefficients are negative numbers ranging from -1.00 (perfect correlation) to 0.00 (no correlation). In a scatterplot, negative correlation exists if a negative slope is seen

➢ Be sure to remember that CORRELATIONS DO NOT NECESSARILY MEAN CAUSATION.

>>> If car accidents increase with increasing temperatures, it does not necessarily mean that hot temperatures cause more traffic accidents!!

➢ Be aware of ILLUSORY CORRELATION: seeing relationships between something when there is none.

>>>If you believe that black-colored dogs are more aggressive than white-colored dogs, then you will be more likely to notice and recall events where black-colored dogs show aggressiveness to confirm your belief (also know as "self -serving bias."

➢ Regression toward the mean: tendency for extreme values to go back ("regress") to the average value (mean).

>>>If you normally get 80% on your tests and suddenly you got an extreme (unusual) score of 50%, then on your next test you are likely to get around 80% again.

➢ Statistical Significance: measure of how likely an event is due to chance alone.

>>> If average marks concerning two classes are statistically significant, then the marks are actually different, not due to random chance or sampling errors.

>>> Statistical significance is usually determined by mathematical analysis of the samples.

GRAPHS (Be Aware Of)

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Perfect positive correlation (+1.00) No relationship (0.00) Perfect Negative Correlation (-1.00)

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Symmetrical Distribution Negatively Skewed Distribution Positively Skewed Distribution

(Bell Curve)

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