Table 5 Subscale and individual item statistics for the IPOS-Dem family member version

Dementia Interaction Impact subscale statistics

Cronbach’s α

Guttman’s λ 6

Average interitem correlation

M

SD

0.83

0.79

0.54

2.06

1.07

Item

n

Item-total correlation

Item-total correlation ^a

Item-total correlation ^b

Item-total correlation ^c

M

SD

Poor mobility

110

0.79

0.79

0.67

0.61

2.01

1.36

Difficulty communicating

114

0.86

0.86

0.81

0.73

2.09

1.41

Lost interest

110

0.8

0.81

0.72

0.64

2.21

1.23

Able to interact

116

0.79

0.79

0.68

0.62

1.94

1.23

Dementia Physical Impact Easy to Assess subscale statistics

Cronbach’s α

Guttman’s λ 6

Average interitem correlation

M

SD

0.84

0.84

0.48

1.52

0.94

Item

n

Item-total correlation

Item-total correlation ^a

Item-total correlation ^b

Item-total correlation ^c

M

SD

Weakness

112

0.83

0.86

0.86

0.78

2.09

1.11

Poor appetite

101

0.76

0.74

0.65

0.6

0.88

1.19

Drowsiness

109

0.82

0.84

0.82

0.75

1.87

1.14

Sleeping problems

65

0.71

0.71

0.62

0.56

0.78

0.89

Swallowing problems

101

0.77

0.7

0.6

0.56

0.88

1.19

Family anxious or worried

115

0.7

0.68

0.58

0.54

1.86

1.24

Dementia Physical Impact Hard to Assess subscale statistics

Cronbach’s α

Guttman’s λ 6

Average interitem correlation

M

SD

0.77

0.86

0.4

0.55

0.74

Item

n

Item-total correlation

Item-total correlation ^a

Item-total correlation ^b

Item-total correlation ^c

M

SD

Shortness of breath

107

0.79

0.71

0.66

0.59

0.44

0.73

Nausea

86

0.7

0.7

0.63

0.51

0.14

0.41

Vomiting

85

0.7

0.79

0.78

0.66

0.05

0.21

Constipation

51

0.7

0.75

0.75

0.56

0.55

0.92

Sore or dry mouth

85

0.89

0.8

0.78

0.75

0.65

0.98

Diarrhoea

46

0.65

0.57

0.47

0.39

0.41

0.78

Dental problems

96

0.73

0.57

0.46

0.42

0.9

1.14

Dementia Behavioural and Emotional Impact subscale statistics

Cronbach’s α

Guttman’s λ 6

Average interitem correlation

M

SD

0.86

0.84

0.61

1.46

0.83

Item

n

Item-total correlation

Item-total correlation ^a

Item-total correlation ^b

Item-total correlation ^c

M

SD

Agitation

111

0.84

0.84

0.77

0.7

1.31

1.03

Anxious or worried

110

0.88

0.89

0.86

0.79

1.49

0.96

Felt depressed

109

0.84

0.84

0.76

0.7

1.57

1.03

Inner peace

106

0.8

0.81

0.7

0.65

1.44

0.93