Answer:
10.56 %
Step-by-step explanation:
Information:
mean = 4 years
standard deviation = 0.8 years
P(x < 3) = ?
using the normal distribution you must follow these steps to calculate P(x < 3):
- you calculate Z with this formula:
Z=(x - μ)/(σ/\(\sqrt{n}\))
where:
x is the raw measurement
μ is the mean
σ is the standard deviation
n is the size of sample
in this case, x = 3 , μ = 4, σ = 0.8, n = 1.
thus:
\(Z = \frac{(3-4)}{\frac{0.8}{\sqrt{1}}}\\\\Z = -\frac{1}{0.8}\\\\Z = -1.25\\\)
from the table of normal distribution attached, we see that our Z value is 0.1056
P(x < 3) = 0.1056
so the probability that a CD will last less than 3 years is 10.56%
