University:
York University
Course:
PSYC 2021 | Statistical Methods I
Academic year:

2024
Views:

316

Pages:

2
Author:

Nick T.

Variability Variability • how spread out the scores are in a distribution -amount of spread of the scores around the mean distributions with the same mean can have very different amounts of spread around the mean distributions with different means can have the same amount of spread around the mean Three Measures of Variability. range • Vouriounce • Standard deviation The Range • the distance covered by the Scores in a distribution - from smallest value to largest vowe based on two scores, not all data an imprecise, unreliable measure of variability * range = Xmax - Xmin * Variance and Standard Deviation • most common and most important measure of variability is the Standard deviation a measure of the Standard, or average, distance from the mean describes whether the Scores are clustered closely around the mean or are widely scattered • Calculation differs for population and Samples • Variance is a necessary companion Concept to standard deviation but not the Same Concept • formulas for Variance and Standard deviation - Sample •Variance (Sample data): S: (x-m) - 1 N-1 •Step 1: determine the deviation deviation is distance from the mean deviation Score = X-M Step 2: Find deviation" a "Sum of deviations" to use as a basis of finding an "average two problems deviations Sum to O ↳ if sum always O, "mean deviation" will always be O •Step 3: remove negative deviations First Square each deviation Score - then Sum the Squared deviations (55) • Step 4: average the squared deviations mean Squared deviation is known as "variance" Variability is now measured in Squared units * population variance equals mean (average) Squared deviation (distance) of the Scores from the population mean • Step 5: -goal: to compute a measure of the "Standard" (average) distance of the scores from the mean variance measures the average Squared distance from the mean adjust for having squared all the differences by taking the square root of the Variance • Standard deviation = variance Participant Decution Deviation (一 1