Answer:
a
The probability that the selected joint was judged to be defective by neither of the two inspectors is 
b
The probability that the selected joint was judged to be defective by inspector B but not by inspector A is 
Step-by-step explanation:
From the question we are told that
The sample size is 
The number of outcome for inspector A is 
The number of outcome for inspector B is 
The number of joints judged defective by both inspector is 
The the probability that the selected joint was judged to be defective by neither of the two inspectors is mathematically represented as

Now

substituting values

So


the probability that the selected joint was judged to be defective by inspector B but not by inspector A is mathematically represented as

Now

substituting values

So


1 x 10-3 make sure the -3 is above the 10.
SOLUTION
Given the question in the image, the following are the solution steps to answer the question.
STEP 1: Write the given set of values

STEP 2: Write the formula for calculating the Standard deviation of a set of numbers
![\begin{gathered} S\tan dard\text{ deviation=}\sqrt[]{\frac{\sum^{}_{}(x_i-\bar{x})^2}{n-1}} \\ where\text{ }x_i\text{ are data points,} \\ \bar{x}\text{ is the mean} \\ \text{n is the number of values in the data set} \end{gathered}](https://tex.z-dn.net/?f=%5Cbegin%7Bgathered%7D%20S%5Ctan%20dard%5Ctext%7B%20deviation%3D%7D%5Csqrt%5B%5D%7B%5Cfrac%7B%5Csum%5E%7B%7D_%7B%7D%28x_i-%5Cbar%7Bx%7D%29%5E2%7D%7Bn-1%7D%7D%20%5C%5C%20where%5Ctext%7B%20%7Dx_i%5Ctext%7B%20are%20data%20points%2C%7D%20%5C%5C%20%5Cbar%7Bx%7D%5Ctext%7B%20is%20the%20mean%7D%20%5C%5C%20%5Ctext%7Bn%20is%20the%20number%20of%20values%20in%20the%20data%20set%7D%20%5Cend%7Bgathered%7D)
STEP 3: Calculate the mean

STEP 4: Calculate the Standard deviation
![\begin{gathered} S\tan dard\text{ deviation=}\sqrt[]{\frac{\sum^{}_{}(x_i-\bar{x})^2}{n-1}} \\ \sum ^{}_{}(x_i-\bar{x})^2\Rightarrow\text{Sum of squares of differences} \\ \Rightarrow10332.7225+657.9225+18591.3225+982.8225+2740.52251+9731.8225+3522.4225+18319.6225+2878.3225 \\ +8163.1225+1417.5225+3925.0225+1321.3225+386.1225+5677.6225+2953.9225+3800.7225 \\ +3209.2225+2565.4225+10537.0225 \\ \text{Sum}\Rightarrow108974.0275 \\ \\ S\tan dard\text{ deviation}=\sqrt[]{\frac{111714.55}{20-1}}=\sqrt[]{\frac{111714.55}{19}} \\ \Rightarrow\sqrt[]{5879.713158}=76.67928767 \\ \\ S\tan dard\text{ deviation}\approx76.68 \end{gathered}](https://tex.z-dn.net/?f=%5Cbegin%7Bgathered%7D%20S%5Ctan%20dard%5Ctext%7B%20deviation%3D%7D%5Csqrt%5B%5D%7B%5Cfrac%7B%5Csum%5E%7B%7D_%7B%7D%28x_i-%5Cbar%7Bx%7D%29%5E2%7D%7Bn-1%7D%7D%20%5C%5C%20%5Csum%20%5E%7B%7D_%7B%7D%28x_i-%5Cbar%7Bx%7D%29%5E2%5CRightarrow%5Ctext%7BSum%20of%20squares%20of%20differences%7D%20%5C%5C%20%5CRightarrow10332.7225%2B657.9225%2B18591.3225%2B982.8225%2B2740.52251%2B9731.8225%2B3522.4225%2B18319.6225%2B2878.3225%20%5C%5C%20%2B8163.1225%2B1417.5225%2B3925.0225%2B1321.3225%2B386.1225%2B5677.6225%2B2953.9225%2B3800.7225%20%5C%5C%20%2B3209.2225%2B2565.4225%2B10537.0225%20%5C%5C%20%5Ctext%7BSum%7D%5CRightarrow108974.0275%20%5C%5C%20%20%5C%5C%20S%5Ctan%20dard%5Ctext%7B%20deviation%7D%3D%5Csqrt%5B%5D%7B%5Cfrac%7B111714.55%7D%7B20-1%7D%7D%3D%5Csqrt%5B%5D%7B%5Cfrac%7B111714.55%7D%7B19%7D%7D%20%5C%5C%20%5CRightarrow%5Csqrt%5B%5D%7B5879.713158%7D%3D76.67928767%20%5C%5C%20%20%5C%5C%20S%5Ctan%20dard%5Ctext%7B%20deviation%7D%5Capprox76.68%20%5Cend%7Bgathered%7D)
Hence, the standard deviation of the given set of numbers is approximately 76.68 to 2 decimal places.
STEP 5: Calculate the First and third quartile

STEP 6: Find the Interquartile Range

Hence, the interquartile range of the data is 116
So in 30 min will hike 2 1/4 miles =9 of those 1/4 miles therefore in 10 min will hike 9/3 =3 of those 1/4 miles = 3/4 of a mile
3/4 mile in 10 min;
(3/4)• 4 = 3 miles in 40 min;
6 miles in 80 min;
9 miles in 120 min;
12 miles in 160 min;
15 miles in 200 min;
18 miles in 240 min or 4 hours
4+4+4+4+4+4=24yd is the perimeter.