This preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full DocumentThis preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: Lab 3 zScores, the Normal Curve, and Computer Graphs of Distributions Learning Objectives Define a zscore. Calculate zscores. State the mean and SD of the Standard Normal Curve. Use tabled values of the normal curve to estimate percentages of a distribution. Graph Distributions. What is a zscore? Zscore defined. A zscore tells the location of an observation in terms of standard deviations from the mean. If a zscore is zero, it’s on the mean. If a zscore is positive, it’s above the mean. If a zscore is negative, it’s below the mean. The value of the zscore tells how many standard deviations above or below the mean it is. A z score of 2 is 2 SDs above; 1 is 1 SD below. Zscore formulas To find a zscore, subtract the mean from the score and divide by the SD. A zscore for a population: A zscore for a sample: σ μ = X z s X X z = Computing zscores from raw scores 5 3 2 2 1 5 3 2 4 .5 8 3 5 4 1.25 8 102 4.5 X X X s X s X X z = Computing zscores What is z? =10, =8, s=4, z = ? A: .5 =8, =10, s=2, z=? A: 1 =20, =15, s=5, z =? A: 1 X X X X X X Computing raw scores from zscores  Formulas To find a raw score, multiply the zscore by the SD and then add the mean. Population formula: Sample formula: μ σ + = z X X zs X + = Computing raw scores from zscores  Examples z s zs X=zs+ 1 3 2 3 52 3 264 2 8 81.5 4 165 X X Computing raw scores What is X?...
View
Full
Document
 Fall '08
 Staff

Click to edit the document details