Posted by **Brittany** on Sunday, February 5, 2012 at 5:58pm.

Sweden is reported to have among the highest percentage of citizens aged 80 years and over, at approximately 5.5 % (i.e. 5.5 % of it's population falls within this age category). Suppose 20 individuals are randomly selected from the population, and X is the number of individuals out of 20 that are 80 or more years old.

a) On average, how many of the 20 individuals would be 80 years old or older?

E(x)=np= 20*0.055= 1.1

is this corrected?

b)What is the probability that less than 2 of the 20 individuals are 80 years old or older?

P(x<2)=P(x=0)+P(x=1)= 0.6980679

is this corrected?

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