Showing posts with label spss. Show all posts
Showing posts with label spss. Show all posts

Monday, May 9, 2011

GOOGLE.ORG Tools for Non-Profits!


from
Google's Philanthropy Arm
"You’re changing the world. We want to help."
Apply for the Google for Nonprofits program and get access to exclusive products and resources to help your organization expand its impact.Learn more about whether your organization is eligible and apply today.

from the Google Nonprofits Blog
Google Apps Highlights , Announcing The Google Earth Outreach Developer Grants Program

Research with GOOGLE DOCS Data Collection & Analysis

Google

from the great people at Google Docs! THANK YOU!

Tuesday, April 6, 2010

SPSS Guide: Counting Responses with Frequency Tables

Using a sample of 25 children's responses about their favorite cereals.  The comma delimited data set is available below.

1a. What percentage are males? Females?

 

          61.54% are male, 34.62% are female.  It looks like, in this data, that one gender value was coded as "1" which is a mistake, and which adds a value to the 25 to equal 26.

1b. Which cereal was preferred by most children?



Data File in comma delimited format:

Cereal,Like,Gift,Gender
Ghostly Shadows,crazy,squirt gun,M
Ghostly Shadows,Like,squirt gun,M
Ghostly Shadows,not part,squirt gun,M
Canary Crunch,not part,ring,M
Turtle Treats,crazy,squirt gun,F
Turtle Treats,crazy,ring,F
Turtle Treats,Like,ring,F
Ghostly Shadows,crazy,ring,m
Canary Crunch,not part,squirt gun,F
Turtle Treats,crazy,squirt gun,F
Ghostly Shadows,Like,ring,F
Canary Crunch,not part,squirt gun,F
Turtle Treats,Like,ring,M
Ghostly Shadows,crazy,whistle,F
Canary Crunch,don't know,ring,M
Turtle Treats,crazy,whistle,F
Turtle Treats,Like,ring,F
Ghostly Shadows,Like,squirt gun,F
Turtle Treats,Like,ring,F
Turtle Treats,crazy,can't decide,M
Canary Crunch,Like,ring,F
Turtle Treats,crazy,squirt gun,M
Ghostly Shadows,Like,ring,F
Turtle Treats,Like,ring,F
Turtle Treats,crazy,ring,F

Thursday, March 25, 2010

Statistical Terminology: Why different statistics are used


Descriptive Statistics

Mean: a measure of the general tendency, calculated by adding all the scores and dividing by the number of scores. The advantage over other measures of tendency is that it uses all scores; disadvantage is that it's influenced by extreme scores. It should be used with interval or ratio levels of measurement.
Mode: A measure of central tendency which is the most frequently occurring score in a distribution.
Median: A measure of central tendency that is the middle score of a set , placed in size order. Advantage: not influenced by extremes; Disadvantage: it doesn't use the arithmetic values of the intervals between scores. It requires an ordinal level of measurement and should be used instead of the mean when the distribution of data on an interval scale is skewed.
Standard Deviation: The square root of the variance. It measures the dispersion of the scores around the mean in a normal distribution.
Variance: A measure of dispersion that is eq. to the sum of the squares divided by the degrees of freedom.
Range: Simplest measure of dispersion; measuring the difference b/n the highest and lowest scores. Sometimes the value 1 is added to the difference to reflect that the range is inclusive of the end points.

Inferential Statistics

t-test: finds the difference b/n means b/n two groups. In a one-sample t-test, observed mean is compared to expected mean of the population.
ANOVA (Analysis of Variance): tests for sig. diff. b/n the means. Same results as t-test.
Repeated Measures ANOVA: successive observations from the same source (dog, or person, such as in a longitudinal study). Another e.g. is when the same person is given a treatment of vodka then tested on memory, then comes back in 5 days and is given a placebo.
Correlation: measure of the relation between two or more variables. Correlation coefficients range from -1.00 (perfect negative correlation - negative correlation!) to +1.00 (perfect positive correlation). A correlation of 0.00 means A LACK OF CORRELATION.
Multiple Regression: analyzes the relationship between several independent (or predictor) variables and a dependent (or criterion) variable.
Factor Analysis: reduces the number of variables, and then detect the structure of relationships between varaibles -- that is, to classify the variables. E.g., if we are set to measure people's satisfaction, and ask in a survey how much they like their hobbies and also how much time they spend on their hobbies, the two varaiable will probably have a HIGH correlation, which mean we are probably being redundant with both variables - best to condense.
One can summarize the correlation between two variables in a scatterplot. A regression line can then be fitted that represents the "best" summary of the linear relationship between the variables. If we could define a variable that would approximate the regression line in such a plot, then that variable would capture most of the "essence" of the two items. Subjects' single scores on that new factor, represented by the regression line, could then be used in future data analyses to represent that essence of the two items. In a sense we have reduced the two variables to one factor.
Discriminant Analysis: used to discriminate between two or more naturally-occurring groups. E.g., a school researcher may try to find out which variables differ b/n groups of students who decide to go to college and those who don't, and figure out which variables (SAT score, GPA, etc) predict each.
Chi Square Test: A test that uses the chi-square statistic to test the fit between a theoretical frequency distribution and a frequency distribution of observed data for which each observation may fall into one of several classes.
f(x) = {1/[2/2 * (/2)]} * [x(/2)-1 * e-x/2]

= 1, 2, ..., 0 <>

where
is the degrees of freedom
e is the base of the natural logarithm, sometimes called Euler's e (2.71...)
(gamma) is the Gamma function


Friday, March 19, 2010

SPSS Review using GSS (General Social Survey) data


First, I am using a free, open-source program named PSPP. You can read about it and download here. as far as I can tell, it is able to perform the functions necessary for the beginning review exercises in the book: SPSS Guide to Data Analysis. Click to download the data file for this book (v. 15, at least).


CH 3: COUNTING RESPONSES

OBJECTIVES
  • Using a frequency table - to summarize info, find errors in data
  • Finding percentage and cumulative percentages
  • Graphical displays with pie and bar charts, and histograms
  • The mode, median, and mean of responses
  • Using the gss.sav data file (General Social Survey)
Mean, Median, and Mode

Mode is the most frequently found value.
  • in the data, 1 7 9 1 4 0 1 1 4 2, the mode is 1 because it appears most frequently.
Median is the middle value when the data are arranged from smallest to highest.
  • for 2 9 1 8 0 3, the median is (0 1 2 3 8 9) 2.5 = even number of data halfway b/n the two middle values, for odd data, the exact one in the middle (0 1 2 3 7 8 9) = 3
Mean is the average value of the data.
  • for 3 5 1 0 2 3, 3+5+1+0+2+3=14/6 (no. of data) = 2.33

Frequency Table: Counting Reponses

Using the gss.sav data, and the variable satjob (job satisfaction),
satjob
Label: JOB OR HOUSEWORK
Type: F1.0
Missing Values: 0, 8, 9
Measurement Level: Ordinal

Value Labels:
0 NAP
1 VERY SATISFIED
2 MOD. SATISFIED
3 A LITTLE DISSAT
4 VERY DISSATISFIED
8 DK
9 NA
we find this frequency table, describing the data from the GSS