Statistics for the Social Sciences Psychology 340 Spring 2009 Review of SPSS basics

Statistics for the Social Sciences Let’s get some data On a sheet of paper (that you’ll turn in) write out these pieces of information: –Male or female –Height (in inches) –How many pairs of shoes in your closet –Typical number of servings of soda per day –Typical number of servings of water per day –Which day of the week is your busiest? –On a scale of 1 (“hate it”) to 7 (“love it”) rate how you feel about statistics

Statistics for the Social Sciences Basic Concepts  Variable –A condition or characteristic that can have different values  Value –A possible number or category that a score can have  Score –A particular person’s value on a variable

Statistics for the Social Sciences Using SPSS The nature of your data determines how you enter the data into SPSS –The nature of your variables Scales of measurement –The design of a study Are the variables independent or dependent (related)

Statistics for the Social Sciences Brief review of SPSS Two view windows: Data view This is where you type in all of the data To switch between the views click on the tabs

Statistics for the Social Sciences Brief review of SPSS Two view windows: Variable view This is where you specify the details about the variables

Statistics for the Social Sciences The Data View Each row corresponds to an experimental unit (called “cases” in SPSS lingo) So each column in the data view corresponds to a row in the variable view Each column corresponds to a variable

Statistics for the Social Sciences Entering Data into SPSS I recommend that you start by defining your variables and their properties in the variable view Alternative – can enter data first, SPSS will set up the variables, but it may not get all the properties correct.

Statistics for the Social Sciences Variable view Name of the variable Type of variable: numeric, text, monetary, date, etc.

Statistics for the Social Sciences Categorical variables in SPSS SPSS ‘likes’ numbers for analyses –If you plan to analyze a variable, enter it in as a number –If it is categorical (nominal or ordinal) you can label the values (give SPSS names to go along with the numbers) This includes Levels of between groups Independent variable

Statistics for the Social Sciences Levels (scales) of measurement The correspondence between the way you measure the variable and the variable (i.e., what your observations mean) Impacts what kind of statistics you can do, what kind of comparisons you can make

Statistics for the Social Sciences Levels (scales) of measurement Nominal Scale: Consists of a set of categories that have different names. –Measurements on a nominal scale label and categorize observations, but do not make any quantitative distinctions between observations. –Example: Eye color: blue,green, brown,hazel

Statistics for the Social Sciences Levels of measurement Ordinal Scale: Consists of a set of categories that are organized in an ordered sequence. –Measurements on an ordinal scale rank observations in terms of size or magnitude. –Example: T-shirt size: Small,Med,Lrg,XL,XXL

Statistics for the Social Sciences Levels of measurement Interval Scale: Consists of ordered categories where all of the categories are intervals of exactly the same size. –With an interval scale, equal differences between numbers on the scale reflect equal differences in magnitude. –Ratios of magnitudes are not meaningful. –Example: Fahrenheit temperature scale 20º40º “Not Twice as hot”

Statistics for the Social Sciences Levels of measurement Ratio scale: An interval scale with the additional feature of an absolute zero point. –With a ratio scale, ratios of numbers DO reflect ratios of magnitude. Ratio versus interval: Ask what a score of zero means on your scale. If it is the absence of that variable then you have a ratio scale. SPSS doesn’t distinguish between these, collapses them into ‘scale’ measurements

Statistics for the Social Sciences Levels of measurement What kind of measurement is used for each of these variables?: –Male or female –Height (in inches) –How many pairs of shoes in your closet –Typical number of servings of soda per day –Typical number of servings of water per day –Which day of the week is your busiest? –On a scale of 1 (“hate it”) to 7 (“love it”) rate how you feel about statistics

Statistics for the Social Sciences Distributions The data that we have entered into our SPSS files form distributions. Each column of information in the data view corresponds to the scores of a variable for the individuals in our sample. Next week we’ll review descriptive statistical procedures used to describe distributions like these.

Statistics for the Social Sciences In-class lab With the remaining time, go ahead and work through the lab –A few study descriptions, using the decision tree try to determine the appropriate statistical test –Download the “majors.sav” datafile and open it up in SPSS.