Answer:
A.) the number of fencers that do not use the foil as their main weapon
B.) X : 0, 1, 2, 3,..., 21
C.) X ~ p(X) ; 21 ~ 0.4
D.) 21 ~ 0.4
E.) 0.0895
F.) Yes. The probability of all 21 fencers not using the foil as their main weapon is small (less than 1%)
Step-by-step explanation:
A.) since it is reported that 60% of fencers use the foil as their main weapon ;
The random variable (x) : number of fencers that do not use foil as their main weapon ;
( 100% - 60%) = (1 - 0.6) = 0.4
B.) values that X may take on :
Sample size = 21 ;
X : 0, 1, 2,..., 21
The distribution of X
X ~ B ; X ~ p(X) ; 21 ~ 0.4
Part (d) How many fencers are expected to not use the foil as their main weapon?
X * p(x)
21 * 0.4
= 8.4
= 8 (nearest whole number)
Part (e) Find the probability that eleven do not use the foil as their main weapon.
P(x = 11)
Using the binomial probability relation :
P(x =x) = nCx * p^x * (1 - p)^(n - x)
P(x = 11) = 21C11 * 0.4^11 * 0.6^10
P(x = 11) = 0.0895
Part (f) Based on numerical values, would you be surprised if all 21 did not use foil as their main weapon?
P(x = 21) = 21C21 * 0.4^21 * 0.6^0
P(x = 21) = < 0.00001 ( approximately 0)
Hence, based on this very low value which is almost equal to 0 ; it will be surprising if all 21 do not use foil as their main weapon
