There are no universally agreed determinants are outliers.
Commonly used measure are
Lower Outer Fence : Q1 - 3*IQR
Lower Inner Fence : Q1 - 1.5*IQR
Upper Inner Fence : Q3 + 1.5*IQR
Upper Outer Fence : Q3 + 3*IQR
where Q1 and Q3 are the lower and upper quartiles and IQR = Q3 - Q1.
Values further than the outer fence are called extreme outliers while those between the inner and outer fences are mild outliers.
On that basis the values 2 and 3 are both mild outliers.
19. It is prime.
2,870,795,128,037,760 or approx 2.871*1015
16/19
In the example provided, the quartiles are: 25% = 16.5 (the median of {15, 16, 17, 18}) 50% = 18.5 (the median of {15, 16, 17, 18, 19, 20, 21, 22}) 75% = 20.5 (the median of (19, 20, 21, 22})
1.1053
Mean (12, 18, 19, 20, 21) = 18
16 + 16 + 16 + 17 + 18 + 18 + 18 + 19 + 19 + 20 + 20 + 20 + 21 = 238
20.37 is the mean.
19. It is prime.
Just over 20 18 + 19 + 21 + 23 = 81 81 / 4 (numbers) = 20.25
2,870,795,128,037,760 or approx 2.871*1015
16/19
The minimum drinking age in Connecticut was lowered from 21 to 18 in 1972. It was raised from 18 to 19 in 1982, raised from 19 to 20 in 1983, and raised from 20 to 21 in 1985.
1
19 is Joe and 21 is Kevin
No number appears more than once, so there is no mode.
All the numbers are composite except the ones in bold: 18 19 20 21 22 23 24 25.