PSY202-210793516

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Concepts:

Contents

Dependent Variable

Definition: According to the textbook, a dependent variable is the variable in the study which is being measured.

Example: Shoe Pain

Application: In the study, the experimenters tested which shoes caused the most pain. As pain was the variable that was measured, pain was the dependent variable.

Nominal Variable

Definition: According to the textbook, a nominal variable is the variable that has different categories of some qualitative aspect.

Example: Shoe Pain

Application: In the study, the experimenters tested which shoes caused the most pain. The variable "type of shoe" is a nominal variable because it is a qualitative measurement involving different categories.

Ordinal Variable

Definition: According to the textbook, a ordinal variable is a variable who's properties are ranked in order of magnitude which are mutually exclusive and exhaustive.

Example: http://www.rti.org/news.cfm?nav=34&objectid=97CE3EE9-5822-4965-B2541686DB91360E

Application: In this study, the variables are the 9th grade year for the students of 2009, followed by when they become 11th graders, and then in their post secondary years are the 3 ordinal variables because it is a rank of academic standing.

Interval Variable

Definition: Accordingto the textbook, an interval variable is a variable that posseses a given distance between measures which has the same meaning anywhere on the scale.

Example: http://www.scholarpedia.org/article/Operant_conditioning#SkinnerBox

Application: In Figure 2: A Skinner Box, every 60 seconds or so, on average, the response key (K) lights up for 7 s in which it let's the bird know to come out to eat. The interval variable is the 60 seconds the response key lighting for 7 s because it has a given distance between measures.

Ratio Variable

According to the textbook, a ratio variable is a variable which has an absolute zero and possesses all the properties of and interval scale.

Example: http://circoutcomes.ahajournals.org/cgi/content/abstract/2/1/9

Application: The ratio variable is the elapsed time of less than 15 minutes to minimize the time of treatment with patients with cardiac arrest symptoms. The ratios has an absolute zero point with elapsed time.

Frequency Distribution (regular, grouped, relative, or cummulative)

According to the te xtbook, a frequency distribution is a table of observations of unordered scores presented in order of occurence, tally mark a record for each score of the new ordered list, and then convert the tallies to numbers.

Example: http://www.census.gov/cmpendia/statab/cats/health_nutrition/_insurance.html

Application: In the PDF464k under number 150 shows a frequency distribution of U.S workers participating in health care benefits. Since there are many variables much variation the author chose to use a frequency distribution.

Percentile (percentile or percentile rank)

According to the textbook, a percentile is a system used to show how an individual has performed relative to a known group which is based on the cummulative percentage distribution.

Example: http://www.usnews.com/blogs/college-rankings-blog/2009/10/08/which-schools-are-a-for-b-students.html

Application: The percentiles shown at the bottom of the article are SAT 75th percentile less than or equal to 1350 because it shows a rank relatively compared to the other students. This statistic is for the best A schools for B students, as the author stated in the article.

Histogram

Definition: According to the textbook, a histogram is a graph that consists of heights which represent frequency or relative frequency symbolized by a series of rectangles.

Example: http://www.srl.caltech.edu/ACE/ACENews/ACENews4.html

Application: This histogram shows the frequencies with bars and without spaces of collected measurements of elemental and ionic charge state composition of energetic particle fluxes.

Frequency Polygon

According to the textbook, a frequency polygon is a series of dots at the midpoint of every class interval and which the height represent the height of the frequency or relative frequency of each dot.

Example: http://money.cnn.com/?cnn=yes

Application: This frequency polygon shows a series of years from 2009 to 2009 of the percentage of U.S. people who are unemployed.

Bar Diagram

Definition: According to the textbook, a bar diagram is used for qualitative data with space between the rectangles is similar to a histogram.

Example: http://thechronicleherald.ca/pdfs/worldseriesprimer.pdf

Application: At the very top of this pdf file shows the batting average for the regular seasond of baseball teams with a bar graph. It is presented in seperate non attached blue and red bars.

Pie Chart

Definition: According to the textbook, a pie chart is used for qualitative data and each piece shows a relative frequency of a category.

Example: http://www.warresisters.org/pages/piechart.htm

Apllication: It shows where you incoem tax money really goes and is presented by different colors for each category with a percentage for each.

Mean

Definition: According to the textbook, the mean is the sum of all the scores divided by the total number of scores.

Example: http://thechronicleherald.ca/pdfs/worldseriesprimer.pdf

Application: The batting averages or means are shown for the Phillies and Yankees towards the middle bottom of the page. Such as for example a .255 batting average or mean for Phillies catcher Carlos Ruiz during 37 games.

Median

Definition: According to the textbook, a median is the point which has half the scores below the scale of a distribution and half the scores above it.

Example: http://www.theolympian.com/news/story/1059067.html

Application: The median sales price of a Thurston County home last month was $225,000 which means that half the prices are below and half the prices are above. For example, since November 2008 the median prices for houses in that area fell from $246,900 to $225,000 last month.

Mode

Definition: According to the textbook, a mode is the score which occurs with the greatest frequency.

Example: http://www3.interscience.wiley.com/cgi-bin/fulltext/121670693/PDFSTART

Application: In this pdf file the lowest score under submissive is 2.71 and the hightest score is 5.56 and subtracting the two gives you a range of 2.85

Range

Definition: According to the textbook, a range is the simplest form of measurement which is the difference between the highest and lowest scores.

Example: http://www.nationalpost.com/cars/story.html?id=2301860

Application: The author of this article is describing how the new 2012 Chevrolet Volt and how its Volt relies solely on its battery and only uses the engine to extend the vehicle's driving range unlike the

Variance

Definition: According to the textbook, variance is the mean of the squares of the deviation scores.

Example: http://brfss.arkansas.gov/pdf/youth_surveys/2007%20Howard%20CYHS%20Frequency%20Tables.pdf

Application: For table 4 the frequencies are 545, 7, 5, 2, and 2. We need to subtract each number by the total 716 and we get -16, -554, -556, -559, -559. We then sum all those scores and we get 0. We then square each value and we get 256, 306916, 309136, 312481, and 312481. We then sum each squared value and we get 1,241,270. Lastly, we divide by the total number of frequencies, n=5, and we get 248,254.

Standard Deviation

Definition: According to the textbook, a standard deviation is the square root of the variance which obtains wide variability.

Example:http://brfss.arkansas.gov/pdf/youth_surveys/2007%20Howard%20CYHS%20Frequency%20Tables.pdf

Application: From the previous application answer of 248,254, we simply have to square root it to get a standard deviation of 498.2509

Standard Scores (z-scores)

Definition: According to the textbook, the standard score or, or z-score, uses the standard deviation as the unit of measurement to state the position of a score in relation to the mean of the distribution.

Example: http://brfss.arkansas.gov/pdf/youth_surveys/2007%20Howard%20CYHS%20Frequency%20Tables.pdf

Application: The z-score for a sample is z= score - sample mean/standard deviation of sample. So if we look at the first score from table 4 use the standard deviation from the prevoius example and apply this formula, we get 545-716/498.2509= -0.3432, which is our z-score.

Scatterplot

Definition: According to the textbook, a scatterplot is a diagram with each point representing a single case and then shows the scores on the two variable for that case.

Example: http://www.orthosupersite.com/view.asp?rID=50760

Application: The line on the graph from Fig.4 shows the peak temperature decreases as the increasing of hemoglobin loss with the line facing up to teh left making it a negative correlation.

Correlation (r)

Definition: According to the textbook, a correlation (r) is a symbol for Pearson's coefficient of correlation which is a measure of the degree between the relationship of two variables.

Example: http://www.orthosupersite.com/view.asp?rID=50760

Application: The correlation between the two variables peak temp. and hemoglobin loss is negative as presented by the line going up to the left.

EXTRA CREDIT: Correlation does not equal causation

http://www.cnn.com/2009/HEALTH/10/30/oversleeping.health.effects/index.html

The article explains that sleeping excessively will make you feel tired and groggy when waking up.

A third possible variable is that the individual sleeping for 12 hours was tossing and turning all night and therefore had poor quality sleep.

EXTRA CREDIT : Critically Evaluating Research

Guideline 3 Definition: One form to critically evaluate research is to watch out for confounding variables.

Example: http://www.privatemdlabs.com/news/Cancer_Detection_and_Tumor_Markers/Studies:-Colorectal--breast-cancers-linked-to-smoking$19497279.php

Application: A confound may be that the women were probably going to have Cancer regarless of the smoking through heredity.

EXTRA CREDIT: Critically Evaluating Research

Guideline 6: Consider the Setting and wording.

Example: http://www.protectmarriage.com/about/why

Application: This propositions had very confusing wording. People who wanted to vote FOR the right with whomever you chose to marru may have mistankingly voted as Yes0n Prop8. The website for Yes on Prop 8 says to protect marriage which really means to protect the traditional marriage between a man and a woman. NO on Prop. 8 really means to vote to marry which ever sex you choose.

EXTRA CREDIT: Critically Evaluating Research

Guideline 2: Consider teh Source.

Example: http://www.tobacco.org/news/265514.html

Application: The researcher will be biased to say that Tobacco is goog for you blood vessels since it is funded by the Tobacco Institute. The results from the study were therepeutic effects for blood vessel growth from nicotine use.

EXTRA CREDIT: Critically Evaluating Research

Guideline 5: Confounding Variables

Example: http://health.usnews.com/articles/health/healthday/2009/12/08/soy-beneficial-for-breast-cancer-survivors-study.html

Apllication: The author of this article says that women who consume soy on a regulat basis may have a reduced risk of breast Cancer. It does not state however, what other emasures this women took on order to prevent ir reduce teh risk of breast Cancer. Maybe, they took other preventive measures to reduce risk which reallt helped even though they soy was consumed on a regular or daily basis.

EXTRA CREDIT: Critically Evaluating Research

Guideline 3: Sampling metthod

Example: http://abclocal.go.com/kabc/story?section=news/health&id=7160170

Application: The stress that rats face are different than the stress that humans face.







◄ Back to Descriptive Statistics PSY 202 Fall 2009 page

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