A twitching eye can be one sign of stress, especially when it is related to vision problems such as eye strain (see below). Reducing the cause of the stress can help make the twitching stop. Tiredness: A lack of sleep, whether because of stress or some other reason, can trigger a twitching eyelid.
C(n,k) is the number of combinations you can make of k objects out of a given set of n objects. We see that C(n,0) and C(n,n) should be equal to 1, but they require that 0! be used. So 0! = 1 neatly fits what we expect C(n,0) and C(n,n) to be.(n,k) is the number of combinations you can make of k objects out of a given set of n objects. We see that C(n,0) and C(n,n) should be equal to 1, but they require that 0! be used. So 0! = 1 neatly fits what we expect C(n,0) and C(n,n) to be.
1 variable. 2  Ratio variables are interval variables, but with the added condition that 0 (zero) of the measurement indicates that there is none of that variable. 3  So, temperature measured in degrees Celsius or Fahrenheit is not a ratio variable because 0C does not mean there is no temperature.