Answer:
The probability that Delta car batteries last between three and four years
P(36≤X≤48) = 0.5188
The percentage of that Delta car batteries last between three and four years
P(3≤X≤4) = 52%
Step-by-step explanation:
Step(i):-
Given that the sample size n =12 -volt car batteries
Let 'X' be a Random variable in a normal distribution
Given that mean of the normal distribution = 45 months
Given that the Standard deviation of the normal distribution = 8months
Step(ii):-
Let X₁ = 3 years = 12 × 3 = 36 months
[tex]Z_{1} = \frac{x_{1} -mean}{S.D} = \frac{36-45}{8} = -1.125[/tex]
Let X₂ = 4 years = 12 × 4 = 48 months
[tex]Z_{2} = \frac{x_{2} -mean}{S.D} = \frac{48-45}{8} = 0.375[/tex]
Step(iii):-
The probability that Delta car batteries last between three and four years
P(36≤X≤48) = P(-1.125≤Z≤0.375)
= P(Z≤0.375) - P(Z≤-1.125)
= 0.5 +A(0.375) - (0.5-A(1.125)
= 0.5 + 0.1480 - (0.5 -0.3708)
= 0.1480 + 0.3708
= 0.5188
Final answer:-
The probability that Delta car batteries last between three and four years
P(36≤X≤48) = 0.5188
The percentage of that Delta car batteries last between three and four years
P(3≤X≤4) = 52%
