Statistical Methods for Psychology

Section 7.3 Testing a Sample Mean When sIs Unknown—The One-Sample tTest 189

Table 7.1 Data and plots for LBW infants on Psychomotor Development
Index (PDI)

Boxplot

Raw Data
96 120 112 100
125 96 86 124
89 104 116 89
127 89 89 124
102 104 120 102
112 92 92 102
120 124 83 116
108 96 108 96
92 108 108 95
120 86 92 100
104 100 120 120
89 92 102 98
92 98 100 108
89 117 112 126

Mean 5 104.125
S.D. 5 12.584
N 556

Stem-and-Leaf Display

Stem Leaf

8* 3

8. 6 6 9 9 9 9 9 9
   9* 2 2 2 2 2 2


9. 5 6 6 6 6 8 8
   10* 0 0 0 0 2 2 2 2 4 4 4


10. 8 8 8 8 8
    11* 2 2 2


11. 6 6 7
    12* 0 0 0 0 0 0 4 4 4


12. 5 6 7

–2 –1 0 1 2

120

110

100

90

Theoretical Quantiles

Q-Q Plot of Low-Birthweight Data

Sample Quantiles