January

0.27

1.75

1.48

February

1.77

2.45

0.68

March

5.84

7.15

1.31

April

11.68

13.2

1.52

May

16.92

17.6

0.68

June

21.93

23.25

1.32

July

24.79

25.75

0.96

August

24.02

24.3

0.28

September

19.98

21.65

1.67

October

13.89

15.05

1.16

November

8.77

7.35

−1.42

December

3.06

4.4

1.34

Mean

12.74

13.66

0.91

P(T ≤ t) two-tail^**

0.80283627