Table 4 Descriptive statistics of the total sample, test of gender differences, bivariate correlations between individual ISI items, and item-total correlations among male and female young adults

Item 1

0.67

0.93

0-4

1.45

1.76

5.67*

.007

---

---

Item 2

0.66

0.92

0-4

1.47

1.80

9.46**

.011

---

---

Item 3

0.49

0.86

0-4

1.90

3.13

0.95

.001

---

---

Item 4

1.09

1.04

0-4

0.82

0.03

2.61

.003

---

---

Item 5

1.71

1.01

0-4

0.28

−0.57

1.63

.002

---

---

Item 6

1.38

1.01

0-4

0.34

−0.56

1.79

.002

---

---

Item 7

0.57

0.91

0-4

1.57

1.64

1.48

.002

---

---

ISI total score

6.56

4.31

0-26

1.09

1.35

6.88**

.008

4.67

.073

Bivariate correlations

Item 1

Item 2

Item 3

Item 4

Item 5

Item 6

Item 7

Item 1

---

.40***

.20**

.63***

.19**

.05

.58***

Item 2

.39***

---

.42***

.59***

.16*

.11

.47***

Item 3

.30***

.48***

---

.36***

.10

.10

.29***

Item 4

.67***

.51***

.41***

---

.22**

.10

.70***

Item 5

.28***

.20***

.17***

.26***

---

.52***

.29***

Item 6

.06

.07

.06

.09*

.47***

---

.15*

Item 7

.56***

.47***

.32***

.64***

.42***

.25***

---

r_it

.57***

.52***

.42***

.65***

.45***

.25***

.69***