PSY202-300476701
From PsychWiki - A Collaborative Psychology Wiki
Concepts:
Dependent Variable
Definition: According to the text book, a dependent variable is the variable being measured.
Example: http://abcnews.go.com/GMA/exercise-boost-brainpower/story?id=8840026
Apply: The dependent variable in the study is brain power. Hillman was measuring the increase of brain activity after exercising.
Nominal Variable
Ordinal Variable
Interval Variable
Ratio Variable
Frequency Distribution (regular, grouped, relative, or cummulative)
Definition: According to the book a frequency distribution shows the number of observations for the possible categories or score values in a set of data.
Example: http://content.usatoday.com/sportsdata/basketball/ncaab/usc/stats
Application:
Percentile (percentile or percentile rank)
Histogram
Definition: According to the textbook a histogram is a graph that consist of a series of rectangles the heights represent the frequency or relative frequency.
Example:http://media.techtarget.com/digitalguide/images/Misc/iw_histogram.gif
Application: The rectangles show the frequency of score for a particular test.
Frequency Polygon
Definition: According to the textbook a frequency polygon is a graph that consist of a series of connected dots above the midpoint of each possible class interval.
Example: http://upload.wikimedia.org/wikipedia/commons/0/02/HistFreqPoly.JPG
Application: The frequency distribution shows the midpoints for each group of data. It is best used when comparing two data sets.
Bar Diagram
Definition: According to the textbook a bar diagram is used for qualitative data, it similar to the histogram, except spaces are in between each rectangle.
Example: http://www.neuroscience.com/graphic.html
Application: The bar graph represents qualitative data.
Extra Credit:
Definition: According to the textbook a bar diagram is used for qualitative data, it similar to the histogram, except spaces are in between each rectangle.
Example:http://www.usatoday.com/news/washington/2009-12-03-poll-afghan-strategy_N.htm?loc=interstitialskip
Application: The data collected by USA Today is presented in a bar graph. It shows how worried Americans are about the cost of the war. This violates the rule number 7. USA presented the data as a bar graph but it best represents a histogram. There should be space between the rectangles and the data is not quantitative.
Pie Chart
Definition: According to the textbook a pie chart is used for qualitative data are in any piece of the pie shows the relative frequency.
Example: start1.jpl.nasa.gov/ images/techPieChart.gif
Application:
Mean
Definition: According to the textbook the mean is the sum of all score dived by the total number of scores.
Example:http://www.foxbusiness.com/story/markets/industries/energy/oil-price-average--barrel-winter-eia/
Application: THe average price of a barrel of oil is $76. I pay around 40 dollars every time I feel up my New Beetle!! I am paying for 53 percent of one barrel. By looking at the data I figure the oil industry is ripping me off. I hope the techron they put in the 91 grade are costly. If not Chevron is making a big profit off it customers.
Median
Definition: According to the textbook the median is the value that divides the distribution into halves.
Example:http://news.smh.com.au/breaking-news-national/australias-median-age-rising-abs-20091209-kj2x.html
Application: The article reports the median of age for women in Australia has risen. Yet they report no variable that increased the median.
Mode
Definition: According to the textbook the mode is the score that appears with the greatest frequency.
Example:
Range
Variance
Standard Deviation
Standard Scores (z-scores)
Definition: according to the textbook the z-score states how far a score is from the mean in standard deviation units.
Example:http://www.dailynews.lk/2009/11/27/news04.asp
Application: The z-score represent the the score of each person and where they fall into ranking.
Scatterplot
Definition: According to the textbook a scatterplot is a graph of a bivariate distribution consisting of dots at the point of intersection of paired scores.
Example: start1.jpl.nasa.gov/ images/techPieChart.gif
Application: Use a scatterplot for a single case with two variables. Its easier to visually to determine correlation.
Correlation (r)
Definition: According to the textbook correlation is a measure of the degree of relationship between two variables.
Example: http://abcnews.go.com/GMA/exercise-boost-brainpower/story?id=8840026
Application: Hillman's study tries to show the relationship between exercise and brain power. He concludes that frequent exercising can increase a person's brainpower.
EXTRA CREDIT: Correlation does not equal causation
Example: http://abcnews.go.com/GMA/exercise-boost-brainpower/story?id=8840026
Application: Hillman's result are miss leading. He is saying exercise increases brain power. I would say the correlation is weak. Exercise does not consistently or greatly increase brain power.
◄ Back to Descriptive Statistics PSY 202 Fall 2009 page
