Answer:
a. ![f_X(x) = \dfrac{1}{3.5}8.5](https://tex.z-dn.net/?f=f_X%28x%29%20%3D%20%5Cdfrac%7B1%7D%7B3.5%7D8.5%3Cx%3C12)
b. the probability that the battery life for an iPad Mini will be 10 hours or less is 0.4286 which is about 42.86%
c. the probability that the battery life for an iPad Mini will be at least 11 hours is 0.2857 which is about 28.57 %
d. the probability that the battery life for an iPad Mini will be between 9.5 and 11.5 hours is 0.5714 which is about 57.14%
e. 86 should have a battery life of at least 9 hours
Step-by-step explanation:
From the given information;
Let X represent the continuous random variable with uniform distribution U (A, B) . Therefore the probability density function can now be determined as :
![f_X(x) = \dfrac{1}{B-A}A](https://tex.z-dn.net/?f=f_X%28x%29%20%3D%20%5Cdfrac%7B1%7D%7BB-A%7DA%3Cx%3CB)
where A and B are the two parameters of the uniform distribution
From the question;
Assume that battery life of the iPad Mini is uniformly distributed between 8.5 and 12 hours
So; Let A = 8,5 and B = 12
Therefore; the mathematical expression for the probability density function of battery life is :
![f_X(x) = \dfrac{1}{12-8.5}8.5](https://tex.z-dn.net/?f=f_X%28x%29%20%3D%20%5Cdfrac%7B1%7D%7B12-8.5%7D8.5%3Cx%3C12)
![f_X(x) = \dfrac{1}{3.5}8.5](https://tex.z-dn.net/?f=f_X%28x%29%20%3D%20%5Cdfrac%7B1%7D%7B3.5%7D8.5%3Cx%3C12)
b. What is the probability that the battery life for an iPad Mini will be 10 hours or less (to 4 decimals)?
The probability that the battery life for an iPad Mini will be 10 hours or less can be calculated as:
F(x) = P(X ≤x)
![F(x) = \dfrac{x-A}{B-A}](https://tex.z-dn.net/?f=F%28x%29%20%3D%20%5Cdfrac%7Bx-A%7D%7BB-A%7D)
![F(10) = \dfrac{10-8.5}{12-8.5}](https://tex.z-dn.net/?f=F%2810%29%20%3D%20%5Cdfrac%7B10-8.5%7D%7B12-8.5%7D)
F(10) = 0.4286
the probability that the battery life for an iPad Mini will be 10 hours or less is 0.4286 which is about 42.86%
c. What is the probability that the battery life for an iPad Mini will be at least 11 hours (to 4 decimals)?
The battery life for an iPad Mini will be at least 11 hours is calculated as follows:
![P(X\geq11) = \int\limits^{12}_{11} {\dfrac{1}{3.5}} \, dx](https://tex.z-dn.net/?f=P%28X%5Cgeq11%29%20%3D%20%5Cint%5Climits%5E%7B12%7D_%7B11%7D%20%7B%5Cdfrac%7B1%7D%7B3.5%7D%7D%20%5C%2C%20dx)
![P(X\geq11) = {\dfrac{1}{3.5}} (x)^{12}_{11}](https://tex.z-dn.net/?f=P%28X%5Cgeq11%29%20%3D%20%20%7B%5Cdfrac%7B1%7D%7B3.5%7D%7D%20%28x%29%5E%7B12%7D_%7B11%7D)
![P(X\geq11) = {\dfrac{1}{3.5}} (12-11)](https://tex.z-dn.net/?f=P%28X%5Cgeq11%29%20%3D%20%20%7B%5Cdfrac%7B1%7D%7B3.5%7D%7D%20%2812-11%29)
![P(X\geq11) = {\dfrac{1}{3.5}} (1)](https://tex.z-dn.net/?f=P%28X%5Cgeq11%29%20%3D%20%20%7B%5Cdfrac%7B1%7D%7B3.5%7D%7D%20%281%29)
![P(X\geq11) = 0.2857](https://tex.z-dn.net/?f=P%28X%5Cgeq11%29%20%3D%200.2857)
the probability that the battery life for an iPad Mini will be at least 11 hours is 0.2857 which is about 28.57 %
d. What is the probability that the battery life for an iPad Mini will be between 9.5 and 11.5 hours (to 4 decimals)?
![P(9.5 \leq X\leq11.5) =\int\limits^{11.5}_{9.5} {\dfrac{1}{3.5}} \, dx](https://tex.z-dn.net/?f=P%289.5%20%5Cleq%20X%5Cleq11.5%29%20%3D%5Cint%5Climits%5E%7B11.5%7D_%7B9.5%7D%20%7B%5Cdfrac%7B1%7D%7B3.5%7D%7D%20%5C%2C%20dx)
![P(9.5 \leq X\leq11.5) ={\dfrac{1}{3.5}} \, (x)^{11.5}_{9.5}](https://tex.z-dn.net/?f=P%289.5%20%5Cleq%20X%5Cleq11.5%29%20%3D%7B%5Cdfrac%7B1%7D%7B3.5%7D%7D%20%5C%2C%20%28x%29%5E%7B11.5%7D_%7B9.5%7D)
![P(9.5 \leq X\leq11.5) ={\dfrac{1}{3.5}} (11.5-9.5)](https://tex.z-dn.net/?f=P%289.5%20%5Cleq%20X%5Cleq11.5%29%20%3D%7B%5Cdfrac%7B1%7D%7B3.5%7D%7D%20%2811.5-9.5%29)
![P(9.5 \leq X\leq11.5) ={\dfrac{1}{3.5}} (2)](https://tex.z-dn.net/?f=P%289.5%20%5Cleq%20X%5Cleq11.5%29%20%3D%7B%5Cdfrac%7B1%7D%7B3.5%7D%7D%20%282%29)
![P(9.5 \leq X\leq11.5) =0.2857* (2)](https://tex.z-dn.net/?f=P%289.5%20%5Cleq%20X%5Cleq11.5%29%20%3D0.2857%2A%20%282%29)
![P(9.5 \leq X\leq11.5) =0.5714](https://tex.z-dn.net/?f=P%289.5%20%5Cleq%20X%5Cleq11.5%29%20%3D0.5714)
Hence; the probability that the battery life for an iPad Mini will be between 9.5 and 11.5 hours is 0.5714 which is about 57.14%
e. In a shipment of 100 iPad Minis, how many should have a battery life of at least 9 hours (to nearest whole value)?
The probability that battery life of at least 9 hours is calculated as:
![P(X \geq 9) = \int\limits^{12}_{9} {\dfrac{1}{3.5}} \, dx](https://tex.z-dn.net/?f=P%28X%20%5Cgeq%209%29%20%3D%20%5Cint%5Climits%5E%7B12%7D_%7B9%7D%20%7B%5Cdfrac%7B1%7D%7B3.5%7D%7D%20%5C%2C%20dx)
![P(X \geq 9) = {\dfrac{1}{3.5}}(x)^{12}_{9}](https://tex.z-dn.net/?f=P%28X%20%5Cgeq%209%29%20%3D%20%20%7B%5Cdfrac%7B1%7D%7B3.5%7D%7D%28x%29%5E%7B12%7D_%7B9%7D)
![P(X \geq 9) = {\dfrac{1}{3.5}}(12-9)](https://tex.z-dn.net/?f=P%28X%20%5Cgeq%209%29%20%3D%20%20%7B%5Cdfrac%7B1%7D%7B3.5%7D%7D%2812-9%29)
![P(X \geq 9) = {\dfrac{1}{3.5}}(3)](https://tex.z-dn.net/?f=P%28X%20%5Cgeq%209%29%20%3D%20%20%7B%5Cdfrac%7B1%7D%7B3.5%7D%7D%283%29)
![P(X \geq 9) = 0.2857*}(3)](https://tex.z-dn.net/?f=P%28X%20%5Cgeq%209%29%20%3D%20%200.2857%2A%7D%283%29)
![P(X \geq 9) = 0.8571](https://tex.z-dn.net/?f=P%28X%20%5Cgeq%209%29%20%3D%20%200.8571)
NOW; The Number of iPad that should have a battery life of at least 9 hours is calculated as:
n = 100(0.8571)
n = 85.71
n ≅ 86
Thus , 86 should have a battery life of at least 9 hours