here is P(x,t) to P'(x,t), to understand explanations draw age-interval at time 't'.
a)P'(x,t)=(P(x,t)+P(x+1,t))/2
Reason
'(x,t) is the number of peoples at risk at exact age [x,x+1] having Age Last Birthday 'x' & but we have information of P(x,t) with Age Nearest Birthday 'x'. Age Nearest Birthday 'x' means exact age between [x-0.5,x+0.5]
we need age between [x,x+1] so we compare with [x-0.5,x+0.5](Age Nearest Birthday 'x') & [x+0.5,x+1.5](Age Nearest Birthday 'x+1').....
see [x,x+1]=[x,x+0.5]+[x+0.5,x+1]=[x-0.5,x+0.5]/2+[x+0.5,x+1.5]/2
age-interval for Age Next Birthday 'x' is [x-1,x]
try these...........
b)P'(x,t)=P(x+1,t)
c)P'(x,t)=(P(x-1,t)+P(x,t))/2
d)P'(x,t)=(P(x,t)+P(x+1,t))/2
e)P'(x,t)=P(x-1,t)
f)P'(x,t)=(P(x-1,t)+P(x,t))/2
Click to expand...