1 Tutorial 2 GE 5 Tutorial 2  rules of engagement no computer or no power → no lesson no computer or no power → no lesson no SPSS → no lesson no SPSS → no lesson no homework done → no lesson no homework done → no lesson

2 Steps in the research process collecting data: Exproting from LimeSurvey processing and displaying data: SPSS Today an important part: chapter 3 and 5 (standard deviation) (Howitt and Cramer)

3 Content seminar 2 1. Quiz (chapters from Howitt & Cramer) 2. Discussion homework (assignment 1 + 2) 3. Describing variables numerically (chapter Howitt & Cramer) 4. Importing a websurvey (LimeSurvey) 5. SPSS workshop 6. Discussion homework next week

4 1. Quiz

5 Quiz Chapter 1, 2 & 3 Howitt & Cramer Password:

6 2. Discussion homework Questions about! Deadline Friday

7 Describing variables numerically: Averages, variation and spread Introduction Typical scores: mean, median and mode Comparison of mean, median and mode The spread of scores: range, min, max, variance, standard deviation.

8 Measures of central tendency mean or 'arithmetic mean' (page 25-26) median (page 26-27) mode (page 27-28)

9 1. Mean The mean is calculated by summing up all of the scores in a distribution and dividing it by the number of scores. In statistical notation:

10 Statistical notation  Statistics uses basic mathematical  operations and notation, but also some  specific notation: Scores are referred to as X (and Y, etc.). N is the number of scores in a population and n is the number of scores in a sample. The frequently used symbol Σ (Greek capital S) stands for ‘summation’. The summation sign ( Σ ) instructs you to add up a set of scores. The Σ is followed by a symbol or equation that defines what is to be summed. NOW calculate Σ X. Use the formula to calculate the mean nrX

11 3. Mode The mode is the most frequently occurring category

12 Mode  Most frequent value in a distribution

13 Mode

14 2. Median The median is the midpoint of the scores in a distribution when they are listed in order from smallest to largest. The median divides the scores into two groups of equal size.

15 Median  The value in the middle of the distribution

16 Median  The value in the middle of the distribution

17 Mean  The point of balance in the distribution

18 Mean  The point of balance in the distribution

19 Mean  The point of balance in the distribution

20 Mean versus median  Mean and median measure central tendency,  using two different concepts of “middle”: Mean is the balance point of a distribution: defined by distances Median is the midpoint of a distribution: defined by number of scores

21 Calculate the mode, median and the mean of the following scores: 3, 3, 3, 3, 3, 3 0, 0, 0, 0, 0, 0, 0, 0,10, , 331, 331, 332, 335

22 Central tendency and level of measurement modemedianmean nominalYes ordinalYes interval/ratioYes

23 Variability / Dispersion Overview  Variability, spread and dispersion are all terms to describe how similar the values of X are to each other.  The focus will be on four ways to describe variability: minimum & maximum range variance Standard deviation

24 Range Minimum & maximum Range  Calculate the minimum, maximum and range of the following values:  3, 5, 4, 3, 7

25 Variability is necessary next to mean  report marks: mean7,0

26 Variabilility  report marks: mean7,0

27 Range  report marks: range82

28 Range is still not precise enough  report marks: range88

29 Variance Symbols used: s2, insert sigma, var defining formula computational formula (page 32-33): less important frequently used in statistics variance estimate, used for samples (page 34)

30 Standard deviation mean deviation from the mean

31 4. LimeSurvey

32 5. SPSS workshop

33 Data BIG smartie survey 2014 Export from LimeSurvey Import in SPSS Check variables Check cases on outliers and exclude them from a copied dataset Check measurement levels Define missing values

34 Step 1: Export data from LimeSurvey Start Limesurvey Open Button  Responses and Statistics Button (export results to SPSS) Download syntax file and data file

35 Step 2: Import data in SPSS Open the SPSS syntax file downloaded from LimeSurvey (SPSS will start) Adapt line x: fill in (after FILE = ) the name of the data file (including extension and complete path to the file!) and put the name between quotation marks Choose 'Run/All' (or select all and push the green arrow)

36 Variable name and labels name: variable name label: variable labels values: value labels

37 Variable type and measure  Type: numeric: figures (real figures and codes) string: names etc. (no mean calculation etc.) other: less important (dates etc.)  Measure: scale ordinal nominal

38 Defining missing values  Specify missing values to remove missing  answers in your analysis: Go to screen ‘Variable View’ Click on the grey square in [MISSING] column Provide (one or more) missing values Close with [OK]

39 Measures in class SPSS assignment  Measures of central tendency: on different levels of measurement Mean Median Mode  Measures of variability: Range (and minimum and maximum) Variance Standard deviation

40 Data transformations Recoding variables (Recode) Computing new variables (Compute and Count)

41 6. Homework

42 Some terms to remember central tendency mean median mode variability, spread Range Minimum maximum variance outlier …

43 Homework: Assignment 3 See Moodle