PSYC241 Week 6 Fall 2024 PDF

Statistics in Psychology PSYC 241 Week 6 The standard units in statistics & Introduction to SPSS Fall, 2024 Demet Kara, PhD Z-scores An indication of how many standard deviations any one value in a sample is away from the mean It is e...

Statistics in Psychology PSYC 241 Week 6 The standard units in statistics & Introduction to SPSS Fall, 2024 Demet Kara, PhD Z-scores An indication of how many standard deviations any one value in a sample is away from the mean It is equally applicable to anything: time, anxiety, depression, height or any other variable. Why do we need it? The number of standard deviations is a universal scale of measurement Z-scores Z score of 0 = the mean Z score of 1 = 1 SD above the mean Z score of -1 = 1 SD below the mean Normal Distribution & Z-scores  Z-score table Second decimal First decimal Exercise Ahmet’s family earns 15.230 TL per month. The average income in Turkey is 11.500 TL with a SD of 2200 TL. What is the percentage of people who earn more than Ahmet’s family? Exercise Ahmet’s family earns 15.230 TL per month. The average income in Turkey is 11.500 TL with a SD of 2200 TL. What is the percentage of people who earn more than Ahmet’s family? (15230-11500)/2200 = 1.70 So it is… Where does Ahmet’s family income fall? 11500 Where does Ahmet’s family income fall? What is the exact percentage? 11500 15230  Z-score table Second decimal 1.70 First decimal Where does Ahmet’s family income fall? The percentage above Ahmet’s 11500 15230 family income is around 4%  Exercise Source: Khan academy  Exercise Source: Khan academy Important questions about Z-score One sided vs. two sided calculations (tails of the distribution) https://measuringu.com/calculators/pcalcz/ Important questions about Z-score Is this table only for normal distribution? What happens to the percentiles of Z-score in a non-normal distribution? Table given within this slides applies only to normal distributions! If you want to find the percentiles on another distribution (e.g., skewed distributions), you first need to calculate the distribution of the area with another function! Now, let’s run all of these on SPSS First, try to get to know SPSS. Everything works through the ‘Analyze’ menu Descriptive Statistics For counts and percentages Analyse – Descriptive Statistics – Frequencies For means, modes, medians and standard deviations Analyse – Descriptive Statistics - Descriptives Frequencies Frequencies Output Descriptives Descriptives Output Producing Graphs/Charts Checking for normality Checking for normality Checking for normality