psychology 202a advanced psychological statistics september 3, 2015
TRANSCRIPT
Psychology 202aAdvanced Psychological
Statistics
September 3, 2015
The show so far
• Last time we talked about:– variables– distributions– grouping– ways of understanding the shape of a
distribution
Peabody Distribution
Values Frequency
55 – 59 1
60 – 64 2
65 – 69 5
70 – 74 2
75 – 79 4
80 – 84 8
85 – 89 6
90 – 94 8
95 – 99 3
100 – 104 1
Software
• We saw that functions in R tend to use fairly intuitive names (e.g., sort(), stem()).
• We were about to introduce SAS and begin a discussion of descriptive statistics. Let’s do that now.
Ways of understanding shape
• Graphics.
• Descriptive statistics.
Histograms
• A histogram is a picture of the frequency distribution:– group the data (7 to 15 intervals)– identify real limits and midpoints of intervals– draw “histobars” over the intervals– use informative labels
Peabody Distribution
Values Frequency
55 – 59 1
60 – 64 2
65 – 69 5
70 – 74 2
75 – 79 4
80 – 84 8
85 – 89 6
90 – 94 8
95 – 99 3
100 – 104 1
Histograms in R
• hist(Peabody)
• R has done a pretty good job:– informative labels– reasonable number of intervals
• but the limits R chose for the intervals are a little strange
• help(hist)