Central Tendency and Variability Chapter 4. Central Tendency >Mean: arithmetic average Add up all...
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- Slide 1
- Central Tendency and Variability Chapter 4
- Slide 2
- Central Tendency >Mean: arithmetic average Add up all
scores, divide by number of scores >Median: middle score
>Mode: most common score
- Slide 3
- Calculating the Mean >Add up all scores >Divide by number
of scores
- Slide 4
- Calculating the Median >Line up the scores in ascending
order >Find the middle number For an odd number of scores, just
find the middle value. For an even number of scores, divide number
of scores by two. Take the average of the scores around this
position.
- Slide 5
- Calculating the Mode >Line up the scores in ascending order.
>Find the most frequent score. >Thats the Mode!
- Slide 6
- >Do measures of central tendency capture the following slide
adequately?
- Slide 7
- Figure 4-4: Bipolar Disorder and the Modal Mood
- Slide 8
- >An early lesson in lying with statistics Which central
tendency is best: mean, median, or mode? Outliers and the Mean
- Slide 9
- Figure 4-6: The Mean without the Outlier
- Slide 10
- Which Measure of Central Tendency is the Best? >The mean is
most commonly used best for symmetric distributions >The median
is best for a skewed distribution or one with outlier(s), >The
mode is used in 3 cases: One particular score dominates a
distribution Distribution is bimodal or multimodal Data are
nominal
- Slide 11
- Measures of Variability >Range From the lowest to the
highest score >Variance Average square deviation from the mean
>Standard deviation Variation from the sample mean
- Slide 12
- Calculating the Range >Determine the highest score
>Determine the lowest score >Subtract the lowest score from
the highest score
- Slide 13
- >Subtract the mean from each score >Square every
deviation from the mean >Sum the squared deviations >Divide
the sum of squares by N Calculating the Variance
- Slide 14
- >Typical amount the scores vary or deviate from the sample
mean This is the square root of variance Calculating the Standard
Deviation
- Slide 15
- Practice Problem >Age of Classmates? Calculate the mean,
median, mode, standard deviation, and the variance for the age of
the members of your class.
- Slide 16
- Interquartile Range >Measure of the distance between the 1
st and 3 rd quartiles. >1 st quartile: 25th percentile of a data
set >The median marks the 50th percentile of a data set. >3
rd quartile: marks the 75 th percentile of a data set
- Slide 17
- Calculating the Interquartile Range Countries top finishes in
the World Cup omitting countries with a score of 0 1, 1, 2, 2, 2,
2, 2, 2, 2, 2, 4, 6, 8, 10