Chapter 1 Displaying the Order in a Group of Numbers and… Intro to SPSS (Activity 1) Thurs. Aug 22, 2013

The Two Branches of Statistical Methods  Descriptive statistics – Summarize/organize Inferential statistics – Draw conclusions/make inferences

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

Levels of Measurement  Numeric (quantitative) variable – Equal-interval variables Example? – Rank-order (ordinal) variables Example?  Nominal (categorical) variables – Example?

Frequency Tables  Provide a listing of individuals having each of the different values for a particular variable.  e.g., stress ratings of 151 students: 4,7,7,7,8,8,7,8,9,4,7,3,6,9,10,5,7,10,6,8,7,8,7,8,7,4,5,10,10,0,9,8,3,7,9,7,9,5,8,5,0,4,6,6,7,5,3,2,8,5,10,9,10,6,4,8,8,8,4,8,7,3,8,8,8,8,7,9,7,5,6,3,4,8,7,5,7,3,3,6,5,7,5,7,8,8,7,10,5,4,3,7,6,3,9, 7,8,5,7,9,9,3,1,8,6,6,4,8,5,10,4,8,10,5,5,4,9,4,7,7,7,6,6,4,4,4,9, 7,10,4,7,5,10,7,9,2,7,5,9,10,3,7,2,5,9,8,10,10,6,8,3

Steps for Making a Frequency Table Make a list down the page of each possible value, from highest to lowest Go one by one through the scores, making a mark for each next to its value on the list Make a table showing how many times each value on your list is used Figure the percentage of scores for each value

A Frequency Table : Grouped Frequency Table: You decide how many intervals to use, but make them equal intervals!

Frequency Graphs  Histogram  Used for continuous data, so bars can touch  Bar graph used for categorical data – bars don’t touch.

Frequency Graphs  Frequency polygon  Like a histogram, but use points instead of bars  May indicate change over time better

Shapes of Frequency Distributions  Unimodal, bimodal, and rectangular

Shapes of Frequency Distributions  Symmetrical and skewed distributions  Which direction is the tail pointing? Pos/Neg?

Shapes of Frequency Distributions  Normal and kurtotic distributions  Indicates variability of the scores – clustered or spread out?

SPSS Example: Data Entry & Frequencies 1. Open SPSS, choose “Type in Data” when starting a new data file. – Notice the spreadsheet has 2 tabs at the bottom: “data view” and “variable view”. – Data view = where you enter your data and use the menus to analyze data – Variable view = where you provide SPSS info about your variables

SPSS Example: Data Entry & Frequencies 2. Start by clicking the “variable view” tab and we’ll give names to our variables Things to note:  Variable names have a max of 8 characters; don’t use spaces or hyphens (underscores are OK)  “labels” column - give more descriptive labels to variables  “type” column – default is numeric, change to ‘string’ if you use those variables

SPSS Example: Data Entry & Frequencies  “values” column – for numeric variables, can provide names for each value 3. Once variables are named, etc., click tab to go back to ‘data view’ and enter data. 4. What to do w/Missing data?

SPSS Example: Data Entry & Frequencies Once data is entered, begin analyses by using menus at top of ‘data view’ window. 5. For frequency tables, (Analyze  Descriptives  Frequencies) then click on arrow to get variables you want into ‘variable’ list. When analysis is done, SPSS takes you to a new ‘output’ window. Use the window buttons at bottom to move back & forth between output and data. Note – in tables, difference between “Percent” and “Valid Percent” depends on missing data – – Use “Valid Percentage” to report %s & ignore missing data – Use “Percentage” to include all data, even if missing