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

2024
Views:

451

Pages:

3
Author:

Nick T.

Central Tendency Overview •Central tendency - a statistical measure - a single score that defines the center of a distribution purpose: to find the Single Score that is most typical or best represents the entire group The Mean (Interval or Ratio Data) • mathematical center of the data the mean is the sum of all the scores divided by the number of Scores in the data population: M= ΣΧ 2 Sample: M= X example of figuring the mean - it the scores for a particular study were mean =7 M=2x=84/N (17)=7 (10,5,9,8,6,5,9,8,7,6,5,6) 10 10 32 0 MZX/n66/88.25 Learning Check A Sample of n = 12 scores has a mean of M=8. What is the value of Ex for this Sample? α) Σχ =1.5 b) 2x = 4 Σ C) 2x = 20 d) 2x = 96 Characteristics of the Mean •Changing the value of a score changes the mean introducing a new score or removing a Score changes the mean Cunless the score added or removed is exactly equal to the mean) adding or Constant Subtracting a Constant from each Score changes the mean by the same multiplying or dividing each Score by a constant multiplies or divides the mean by that Constant Learning Check A Sample of n=7 Scores has M=5. All of the scores are doubled. What is the new mean? a) M-5 6) M=10 c) M-25 d) More info needed The Median • for skewed interval or ratio data, or ordinal data • the middle Score when all of the Scores are lined up from lowest to highest - for an even number of scores, the median is the average of the two middle Scores • to find the median: - 1) line up all the scores from lowest to highest -2) figure how many scores there are to the middle score by adding I to the number of scores and dividing by 2 -3) Count up to the middle score or scores • the number of rooms in the 7 hotels in downtown Austin is 713, 000, 618,595, 311, 401, and 292. find the medioun Sort in ascending order 292,300,311,401,596, 618,713 (7+1)/2=4 So it is the 4th number Select the middle value MD=401 • the number of tornadoes that have occurred in the U.S. over an Syr period follows. find the median. 684,764,656, 762,856, 1133, 1132, 1303 - find the average of the two middle valves 656,684,702,764, 856, 1132, 1133, 1303 764+856 2 810 (8+1)/2=4.5 so average of the 4th of 5th number Learning Check decide if each of the following Statements is true or false. T/F it is possible for more than 50% of the Scores in a distribution to have values. albove the mean T/F it is possible for more than 50% of the Scores in a distribution to have values albove the median