Since 2002, 4 million visitors plus:
hit counters
search engine optimization service

  Appletcollection Vertical Menu java applet, Copyright 2003 GD

USE OF THE TELLEGEN AND Briggs formula TO DETERMINE the
 Dumont-Willis Indexes (DWI-1  &  DWI-2) for the WISC-IV[1]

Some evaluators have expressed concern that the Full Scale IQ (FSIQ) of the WISC-IV comprises four subtests (40% of the total) that are relatively weak measures of general intellectual ability (Working Memory and Processing Speed: Digit Span, Letter-Number Sequencing, Coding, and Symbol Search) and only six (60%) subtests that measure higher-order intellectual abilities (Verbal Comprehension and Perceptual Organization: Vocabulary, Similarities, Word Reasoning, Block Design, Matrix Reasoning, and Picture Concepts).  Although the WISC-III[2] included four working memory and Processing Speed subtests, only two (20%) of them were included in the FSIQ, and there were eight Verbal Comprehension and Perceptual Organization subtests (80%).  Preliminary clinical experience is suggesting to some evaluators that this shift in balance might be lowering FSIQ scores for children with above-average general intellectual ability and raising FSIQ scores for children with below-average general intellectual ability. 

In this short paper, we provide two alternative composite scores, which are derived, respectively, from the three subtests that enter the VCI and the three subtests that enter the PRI and from the four subtests that enter the WMI and the PSI. We refer to these composites as the Dumont-Willis Indexes (DWIs) in order to distinguish them from the traditional ten-subtest Full Scale IQ, which includes both the six VCI and PRI subtests and the four subtests (i.e., Digit Span, Letter-Number Sequencing, Coding, and Symbol Search) that are not as highly correlated with verbal and non-verbal intelligence as are the six other Verbal and Perceptual subtests, and which load on independent factors in the four-factor solution of the WISC-IV.  The Dumont-Willis Indexes separate the six subtests that are stronger measures of verbal and non-verbal intelligence from the other four subtests.

The DWI-1 score is a six-subtest composite that excludes subtests which load on the WMI and PSI.

The DWI-2 score is a four-subtest composite that includes subtests which load on the WMI and PSI.

Examiners may wish to report DWIs when the Verbal (VCI) and Perceptual (PRI) abilities are found to be close to one another yet significantly different from those of the Working Memory (WMI) or Processing Speed (PSI) abilities.

The tables for the DWIs are provided below. These tables were developed using the WISC-IV subtest intercorrelations (Table 5.1, page 51, WISC-IV Technical and Interpretive Manual[3]) and the Tellegen and Briggs procedure[4].   Conceptually, the Dumont-Willis DWI-1 Index parallels the General Ability Index (GIA) developed by Prifitera, Weiss, and Saklofske[5] and by Tulsky,  Saklofske, Wilkins,  & Weiss[6] for the sum of scaled scores for the VCI and POI subtests of the WISC-III and WAIS-III.  Unlike the DWI tables, the GIA tables are based directly on the WISC-III and WAIS-III normative data. 

Similarly, the Dumont-Willis DWI-2 Index is based on the sum of scaled scores for the Digit Span and Letter-Number Sequencing (WMI) and Coding and Symbol Search (PSI) subtests.  This score is very similar to Alan Kaufman's "third factor"[7] and "SCAD"[8] scores.  It should be computed and considered only when the four WMI and PSI subtest scores are close to one another and substantially separate from the VCI and PRI subtests.  In those cases, the DWI-1 and DWI-2 scores may be an efficient alternative means of summarizing the 10 WISC-IV core subtests, but they must never be confused with normative WISC-IV factor and IQ scores.

To use these tables, first calculate the Dumont-Willis Index 1 Sum of Scaled Scores (DWI-1 SSS) by adding the scaled scores for the following six subtests: Similarities, Vocabulary, Comprehension, Block Design, Picture Concepts, and Matrix Reasoning.

Second, calculate the Dumont-Willis Index 2 Sum of Scaled Scores (DWI-2 SSS) by adding the scaled scores for the following four subtests: Digit Span, Letter-Number Sequencing, Coding, and Symbol Search.

Find the resulting Dumont-Willis Index Sum of Scaled Scores in the column labeled "Sum of DWI- SSS" in the Tables below and read across the row to determine the DWI score, associated percentile rank, and 95% confidence interval (based upon the Standard Error of Estimate).  Be sure to use the "DWI-1: VCI + PRI" table for the six Verbal Comprehension and Perceptual Reasoning subtests (you will see that a SSS of 60 equals a standard score of 100).  Use the "DWI-2: WMI + PSI" table for the four Working Memory and Processing Speed subtests (you will see that a SSS of 40 equals a standard score of 100).

Estimates of overall abilities calculated in this way should always be clearly identified as DWI scores in both text and tables of reports.  These scores must not be confused with the Full Scale IQ, although they may be more useful estimates of intellectual ability in some cases, for example, for some gifted children and for some children with relative weaknesses in working memory and/or processing speed.  For the latter group, the DWIs may help avoid Dumont and Willis's Mark Penalty,[9] the depression of a measure of intelligence by a low score on a measure of a student's specific weakness.  Other children may score significantly higher on the WMI and PSI indices than on the VCI and PSI indices, which may mask important difficulties with conceptual thinking if the FSIQ is used without the DWIs.

We hope these tables prove useful until Prifitera, Tulsky, Saklofske, Weiss, and/or Wilkins provide us with normative data. (for an update see  the additional comments on the use of the DWI1 and DWI2 found at:  Using the DWI or GIA


[1] Wechsler, D. (2003).  Wechsler Intelligence Scale for Children (4th ed.) (WISC-IV).  San Antonio, TX: The Psychological Corporation.
[2] Wechsler, D. (1991).  Wechsler Intelligence Scale for Children (3rd ed.) (WISC-III).  San Antonio, TX: The Psychological Corporation.
[3] Wechsler, D. (2003). WISC-IV Technical and Interpretive Manual. San Antonio, TX: The Psychological Corporation.
[4] Tellegen, A., & Briggs, P. (1967). Old wine in new skins: Grouping Wechsler subtests into new scales.  Journal of Consulting Psychology, 31, 499-506.
[5] Prifitera, A., Weiss, L. G., & Saklofske, D. H. (1998).  WISC-III in context.  In A. Prifitera & D. H. Saklofske (Eds.)  WISC-III clinical use and interpretation: Scientist-practitioner perspectives (pp. 1-38).  San Diego: Academic Press.  
[6] Tulsky, D. S.,  Saklofske, D. H., Wilkins, C., & Weiss, L. G. (2001). Development of a General Ability Index for the Wechsler Adult Intelligence Scale–Third Edition.  Psychological Assessment, 13, 566-571.
[7] Kaufman, A. S. (1979).  Intelligent testing with the WISC-R. New York:  Wiley Interscience.
[8] Kaufman, A. S. (1994).  Intelligent testing with the WISC-III.  New York:  Wiley Interscience.
[9] Willis, J. O. & Dumont, R. P. (2002, pp. 131-132).  Guide to identification of learning disabilities (3rd ed.).  Peterborough, NH: authors.  [http://alpha.fdu.edu/psychology]

Dumont-Willis Index 1 (DWI-1: VCI+PRI)

Sum of DWI-1 SSS

DWI-1 Score

Percentile Rank

95% Confidence Range

 

Sum of DWI-1 SSS

DWI-1 Score

Percentile Rank

95% Confidence Range

Min

Max

 

Min

Max

6

41

1

38

49

 

61

101

53

95

107

7

42

1

39

50

 

62

102

55

96

108

8

43

1

40

51

 

63

103

58

97

109

9

44

1

41

52

 

64

104

61

98

110

10

45

1

42

53

 

65

105

63

99

111

11

46

1

43

54

 

66

107

66

101

112

12

48

1

44

55

 

67

108

68

102

113

13

49

1

45

57

 

68

109

70

103

114

14

50

1

46

58

 

69

110

73

104

115

15

51

1

47

59

 

70

111

75

105

116

16

52

1

48

60

 

71

112

79

106

117

17

53

1

49

61

 

72

113

81

107

118

18

54

1

50

62

 

73

114

82

108

119

19

55

1

51

63

 

74

115

84

109

120

20

56

1

52

64

 

75

116

86

110

121

21

57

1

53

65

 

76

117

87

111

122

22

58

1

54

66

 

77

119

88

112

124

23

60

1

56

67

 

78

120

90

113

125

24

61

1

57

68

 

79

121

91

114

126

25

62

1

58

69

 

80

122

92

115

127

26

63

1

59

70

 

81

123

93

116

128

27

64

1

60

71

 

82

124

95

117

129

28

65

1

61

72

 

83

125

95

118

130

29

66

1

62

73

 

84

126

96

119

131

30

67

1

63

74

 

85

127

96

120

132

31

68

2

64

75

 

86

128

96

121

133

32

69

2

65

76

 

87

129

97

123

134

33

71

2

66

77

 

88

131

97

124

135

34

72

3

67

79

 

89

132

98

125

136

35

73

3

68

80

 

90

133

98

126

137

36

74

4

69

81

 

91

134

99

127

138

37

75

4

70

82

 

92

135

99

128

139

38

76

5

71

83

 

93

136

99

129

140

39

77

6

72

84

 

94

137

99

130

141

40

78

7

73

85

 

95

138

99

131

142

41

79

8

74

86

 

96

139

99

132

143

42

80

9

75

87

 

97

140

99

133

144

43

81

10

76

88

 

98

142

99

134

146

44

83

12

78

89

 

99

143

99

135

147

45

84

13

79

90

 

100

144

99

136

148

46

85

14

80

91

 

101

145

99

137

149

47

86

16

81

92

 

102

146

99

138

150

48

87

18

82

93

 

103

147

99

139

151

49

88

19

83

94

 

104

148

99

140

152

50

89

23

84

95

 

105

149

99

141

153

51

90

25

85

96

 

106

150

99

142

154

52

91

27

86

97

 

107

151

99

143

155

53

92

30

87

98

 

108

152

99

145

156

54

93

32

88

99

 

109

154

99

146

157

55

95

34

89

101

 

110

155

99

147

158

56

96

37

90

102

 

111

156

99

148

159

57

97

39

91

103

 

112

157

99

149

160

58

98

42

92

104

 

113

158

99

150

161

59

99

45

93

105

 

114

159

99

151

162

60

100

50

94

106

 

115

160

99

152

163

 

 

 

 

 

 

116

161

99

153

164

 

 

 

 

 

 

117

162

99

154

165

 

 

 

 

 

 

118

163

99

155

166

 

 

 

 

 

 

119

164

99

156

168

Dumont-Willis Index-2 (DWI-2: WMI+PSI)

Sum of DWI-2 SSS

DWI-2 Score

Percentile Rank

95% Confidence Range

 

Sum of DWI-2 SSS

DWI-2 Score

Percentile Rank

95% Confidence Range

Min

Max

 

Min

Max

4

38

1

35

47

 

41

102

53

96

107

5

40

1

37

48

 

42

103

58

98

109

6

42

1

38

50

 

43

105

63

99

111

7

43

1

40

51

 

44

107

66

101

112

8

45

1

42

53

 

45

109

70

102

114

9

47

1

43

55

 

46

110

75

104

116

10

49

1

45

56

 

47

112

79

106

117

11

50

1

47

58

 

48

114

81

107

119

12

52

1

48

60

 

49

115

84

109

121

13

54

1

50

61

 

50

117

87

111

122

14

55

1

52

63

 

51

119

88

112

124

15

57

1

53

65

 

52

121

91

114

125

16

59

1

55

66

 

53

122

93

116

127

17

61

1

56

68

 

54

124

95

117

129

18

62

1

58

70

 

55

126

95

119

130

19

64

1

60

71

 

56

127

96

121

132

20

66

1

61

73

 

57

129

97

122

134

21

67

1

63

75

 

58

131

97

124

135

22

69

2

65

76

 

59

133

98

125

137

23

71

2

66

78

 

60

134

99

127

139

24

73

3

68

79

 

61

136

99

129

140

25

74

4

70

81

 

62

138

99

130

142

26

76

5

71

83

 

63

139

99

132

144

27

78

6

73

84

 

64

141

99

134

145

28

79

8

75

86

 

65

143

99

135

147

29

81

10

76

88

 

66

145

99

137

148

30

83

12

78

89

 

67

146

99

139

150

31

85

14

79

91

 

68

148

99

140

152

32

86

18

81

93

 

69

150

99

142

153

33

88

19

83

94

 

70

151

99

144

155

34

90

23

84

96

 

71

153

99

145

157

35

91

27

86

98

 

72

155

99

147

158

36

93

32

88

99

 

73

157

99

149

160

37

95

34

89

101

 

74

158

99

150

162

38

97

39

91

102

 

75

160

99

152

163

39

98

45

93

104

 

76

162

99

153

165

40

100

50

94

106

 

 

 

 

 

 

To download template press here.


 

[1] Wechsler, D. (2003).  Wechsler Intelligence Scale for Children (4th ed.) (WISC-IV).  San Antonio, TX: The Psychological Corporation.

[2] Wechsler, D. (2003). WISC-IV Technical and Interpretive Manual. San Antonio, TX: The Psychological Corporation.

[3] Tellegen, A., & Briggs, P. (1967). Old wine in new skins: Grouping Wechsler subtests into new scales.  Journal of Consulting Psychology, 31, 499-506.

[4] Prifitera, A., Weiss, L. G., & Saklofske, D. H. (1998).  WISC-III in context.  In A. Prifitera & D. H. Saklofske (Eds.)  WISC-III clinical use and interpretation: Scientist-practitioner perspectives (pp. 1-38).  San Diego: Academic Press.

[5] Kaufman, A. S. (1979).  Intelligent testing with the WISC-R. New York:  Wiley Interscience.

[6] Kaufman, A. S. (1994).  Intelligent testing with the WISC-III.  New York:  Wiley Interscience.

[7] Willis, J. O. & Dumont, R. P. (2002, pp. 131-132).  Guide to identification of learning disabilities (3rd ed.).  Peterborough, NH: authors.  [http://alpha.fdu.edu/psychology]