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Unit 2 ap psychology Statistics

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Suzanne Taylor

on 10 September 2012

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Transcript of Unit 2 ap psychology Statistics

Unit 2 AP Psychology pt. 2
Statistics and Ethics Statistics Statistics The correlation technique indicates the degree of association between 2 variables
Correlations vary in direction:
Positive association: increases in the value of variable 1 are associated with increases in the value of variable 2
Negative association: increases in the value of variable 1 are associated with decreases in the value of variable 2
No relation: values of variable 1 are not related to variable 2 values Correlational Research © 2004 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 7E Average family income in America.
Average height of women at RCHS.
Average grade on a homework assignment if 2 people didn’t do it. Which is best (mean, median, or mode)? Correlational Research
Research technique based on the naturally occurring relationship between two or more variables
Used to make PREDICTIONS, such as the relation between SAT scores and success at college
Cannot be used to determine cause and effect Just describes sets of data.
You might create a frequency distribution.
Frequency polygons or histograms. Descriptive Statistics Heroin use and grades probably has a negative correlation. Studying and grades hopefully has a positive correlation. Negative Correlation
The variables go in opposite directions. Positive Correlation
The variables go in the SAME direction. Types of Correlation This would be a positive correlation A+ = The measure of a relationship between two variables Correlation pg. 39 This would be a negative correlation = Correlation
Weight Gain Drinking Café Mochas from Dakotas everyday Recording the results from our studies.
Must use a common language so we all know what we are talking about. Statistics Let’s look at the salaries of the employees at Dunder Mifflen Paper in Scranton: $25,000-Pam
$25,000- Kevin
$25,000- Angela
$100,000- Andy
$100,000- Dwight
$200,000- Jim
$300,000- Michael The median salary looks good at $100,000.
The mean salary also looks good at about $110,000.
But the mode salary is only $25,000.
Maybe not the best place to work.
Then again living in Scranton is kind of cheap. Mean, Median and Mode.
Watch out for extreme scores or outliers. Central Tendency Correlations also vary in the strength of the association
Zero correlation: no relationship between the 2 variables
Strong correlation: knowing the value of one variable permits one to accurately estimate the value of the other variable
Strong correlation can be positive or negative
Correlations can be seen in scatter plots Correlations © 2004 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 7E Correlation Difficulties © 2004 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 7E There is a positive correlation between ice cream and murder rates. Does that mean that ice cream causes murder? Detects relationships between variables.
Does NOT say that one variable causes another. Correlational Research A statistical measure of the extent to which two factors relate to one another Measured using a correlation coefficient. How to Read a Correlation Coefficient Why do we have Ethical Guidelines? During WWII the Nazi’s conducted some very unethical studies. Many of their subjects died during theses experiments. What you need to know is:
1. These people were denied the principles in the Belmont Report including being asked to participate. Milgram Study (1963): The Milgram study involved instructing subjects to administer electric shocks to a study confederate in response to poor performance. The subject believed that he/she was involved in a study about learning and memory with each shock intended to affect the learning process. The confederate pretended to be hurt by the shock - in some cases, to the point of losing consciousness; however, he/she did not really feel any shock. The study objective was to assess obedience to authority. This study resulted in significant psychological stress for some subjects including sweating, trembling, stuttering and serious seizures in three subjects. However, in a post-experimental interview, about half of the subjects expressed that they were glad to have participated in the experiment. The question of whether this study was ethical remains open to debate among scholars today. Stanford Experiment
A group of men volunteered for a study and were given the roles of prisoners or guards. In a short time the guards took it upon themselves to start trouble with the prisoners and the experiment got out of hand. Lesson in “the Lucifer” Effect. How good guys turn bad. Respecting the rights of human research participants involves:

Informed consent is an explanation of a study and the responsibilities of experimenter and participant
Deception involving the subjects must be justified
Confidentiality of study information must be maintained
Debriefing refers to explaining the research process to the subjects at the end of the study



Animal research must be justified and must minimize discomfort to participants Ethical Issues in Research © 2004 John Wiley & Sons, Inc.
Huffman: PSYCHOLOGY IN ACTION, 7E Who has to approve ALL research???


IRB
Institutional Review Board (IRB) http://www.blinkx.com/watch-video/amazing-statistics/ERt_t-mY1EwAypRxeXdO_Q A branch of math that summarizes and makes meaningful inferences from the data. Statistics http://www.posterenvy.com/catalog/ms040%20-%20Mean_%20median_modeThumb.jpg Mean is generally used, unless extreme values (outliers) exist — then median is often used, since the median is not sensitive to extreme values. http://www.youtube.com/watch?v=qpxtBghmvvs&feature=related Measures of Central Tendency http://www.youtube.com/watch?v=VuRyosm3t-s Average family income in America.
Average height of women at RCHS.
Average grade on a homework assignment if 2 people didn’t do it. Which is best (mean, median, or mode)? http://rchsbowman.wordpress.com/2010/09/01/statistics-notes-%E2%80%94-measures-of-variation/ Team I has range 6 inches, Team II has range 17 inches.
Disadvantages of the Range
Ignores the way in which data are distributed
Only uses two entries from the data set
Sensitive to outliers
. Range = Maximum – Minimum
                                                                                                                                                Range
Simplest measure of variation
Difference between the largest and the smallest observations Statistical Terms Range
the difference between the highest and lowest scores in a distribution
Standard Deviation
a computed measure of how much scores vary around the mean
Statistical Significance
a statistical statement of how likely it is that an obtained result occurred by chance In a normal distribution, the mean, median and mode are all the same. Normal Distribution http://www.youtube.com/watch?v=xgQhefFOXrM&feature=related Standard Deviatiion http://www.youtube.com/watch?v=pFGcMIL2NVo The formula is easy: it is the square root of the Variance. So now you ask, "What is the Variance?"
Variance
The Variance is defined as:
The average of the squared differences from the Mean.
To calculate the variance follow these steps:
Work out the Mean (the simple average of the numbers) Then for each number: subtract the Mean and square the result (the squared difference). Then work out the average of those squared differences. (Why Square?) Its symbol is σ Standard Deviation pt. 2 http://www.youtube.com/watch?v=pFGcMIL2NVo The formula is easy: it is the square root of the Variance. So now you ask, "What is the Variance?"
Variance
The Variance is defined as:
The average of the squared differences from the Mean.
To calculate the variance follow these steps:
Work out the Mean (the simple average of the numbers) Then for each number: subtract the Mean and square the result (the squared difference). Then work out the average of those squared differences. (Why Square?) Its symbol is σ Standard Deviation pt. 2 A negative z score means a number below the mean. A positive z score means a number above the mean. Z score
A unit that measures the distance of one score from the mean. A skewed distribution represents a set of scores or numbers that is not equal on both sides. Skewed Distributions http://www.sophia.org/identifying-positive-skew/identifying-positive-skew-tutorial?topic=measures-of-shape Negatively skewed distribution (mean<median<mode)
Positively skewed distribution (mean>median>mode) Redelmeier and Tversky (1996) assessed 18 arthritis patients over 15 months, while also taking comprehensive meteorological data. Virtually all of the patients were certain that their condition was correlated with the weather.
In fact the actual correlation was close to zero.
Usually when the data in question stands out Illusory Correlations The number of cavities in elementary school children and vocabulary size are strongly correlated. Skirt lengths and stock prices are highly correlated (as stock prices go up, skirt lengths get shorter). Ice cream sales and the number of shark attacks on swimmers are correlated. The number of cavities in elementary school children and vocabulary size are strongly correlated. Skirt lengths and stock prices are highly correlated (as stock prices go up, skirt lengths get shorter). Ice cream sales and the number of shark attacks on swimmers are correlated. The number of cavities in elementary school children and vocabulary size are strongly correlated. Skirt lengths and stock prices are highly correlated (as stock prices go up, skirt lengths get shorter). Ice cream sales and the number of shark attacks on swimmers are correlated. Outliers skew distributions.
If group has one high score, the curve has a positive skew (contains more low scores)
If a group has a low outlier, the curve has a negative skew (contains more high scores) Distributions http://www.youtube.com/watch?v=oHGr0M3TIcA Calculations that estimate the likelihood that you’d get similar results if you repeated the study; ie, that your results are NOT a fluke or random, atypical event.
Examples:
Class A Test Average: 89.4
Class B Test Average: 87.5
Does Class A really know more or is this just chance? “Inferential Statistics” http://www.youtube.com/watch?v=oHGr0M3TIcA “Inferential Statistics” Infer your data get it infer hahahahaha p value = likelihood that results are a fluke or coincidental
Which should you trust more, results with a low or high p value?
How low?
If p < 0.05, then the results are “statistically significant”.
Statistically significant – not likely due to random chance Inferential Statistics Probability and Significance:
 
Probability, or p, is expressed as a number between 0 and 1. 0 means an event will not happen, 1 means that an event will definitely happen. The P value will always be found to be between 0 and 1 due to the way in which it is calculated. To calculate the probability that a particular outcome will occur, it has to be divided by the number of possible outcomes.
One way to work out the probability of something occurring is to use this formula:
Probability = number of particular outcomes
number of possible outcomes http://www.youtube.com/watch?v=BE54mDs6St4 10 statistics Sampling Probability Correlations Independent is the one you manipulate
Dependent (depends) on the independent Variable Review Let's practice....Mrs. Taylor give out worksheet
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