Stat 101: Lecture 5
Shape
• Symmetry
– Mounded, flat
• Skew
– Right, left
• Other
– Multiple peaks, outliers
1
Histogram of Octane
Histogram of Octane Rating
10
9
8
Frequency
7
6
5
4
3
2
1
0
86
87
88
89
90
91
92
93
94
95
96
Octane
2
Skew - Right
pH of Pork Loins
80
70
Frequency
60
50
40
30
20
10
0
5.0
5.5
6.0
6.5
7.0
pH
3
Stat 101: Lecture 5
Skew - Left
Flexibility Index of Young Adult Men
20
Frequency
15
10
5
0
1
2
3
4
5
6
7
8
9
10
Flexibility Index
4
Multiple Peaks
Size of Diamonds (carats)
Frequency
15
10
5
0
0.1
0.2
0.3
0.4
Size (carats)
5
Center
• A typical value.
• Summary of the whole batch of
numbers.
• For symmetric distributions – easy.
6
Stat 101: Lecture 5
Histogram of Octane
Histogram of Octane Rating
10
9
8
Frequency
7
6
5
4
3
2
1
0
86
87
88
89
90
91
92
Octane
93
94
95
96
Center
7
Spread
• Variation matters.
– Tightly clustered?
– Spread out?
– Low and high values?
8
Comparing Distributions
• How do the distributions compare
in terms of
– Shape?
– Center?
– Spread?
9
Stat 101: Lecture 5
Workout Times
• Who? ISU students.
• What? Time spent working out (minutes),
Gender
• When? 1998.
• Where? Second floor of Leid Recreation
facility.
• How? The time was noted when a student
arrived at the 2nd floor workout area and
when that student left.
10
Workout Times: Men
5
3
Count
4
2
1
30
40
50
60
70
80
90
100
11
Workout Times: Women
5
3
Count
4
2
1
30
40
50
60
70
80
90
100
12