STATISTICS QUIZ

1. Find the standardized variable z if x has Mean 12 and standard deviation 4. (Points : 1)

Question 2.2. Find the area under the standard normal curve to the right of z = 1.65. Round to four decimal places. (Points : 1)

Question 3.3. Find the area under the standard normal curve to the left of z = 2.33 (Points : 1)

Question 4.4. Find the area under the standard normal curve over the interval z = −0.25 to z = 0.25. Compute probabilities using the standard normal table in Appendix B (Table 3). Round the answer to four decimal places. (Points : 1)

Question 5.5. Scores on a certain nationwide college entrance examination follow a normal distribution with a mean of 400 and a standard deviation of 100. Find the probability that a student will score over 500.  Round your answer to four decimal places. (Points : 1)

Question 6.6. Scores on a certain nationwide college entrance examination follow a normal distribution with a mean of 600 and a standard deviation of 100. Find the probability that a student will score between 410 and 700.  Round your answer to four decimal places. (Points : 1)

Question 7.7. A population has mean 53 and standard deviation 12.  Calculate the mean of x bar for a random sample of size 10. (Points : 1)

Question 8.8. A population has mean 69 and standard deviation 8.  Calculate the standard deviation of x bar for a random sample of size 23. (Points : 1)

Question 9.9. Suppose the weights of packages of lettuce coming off a packaging line have a normal distribution with mean 8.4 ounces and standard deviation 0.4 ounce. If every package is labeled 9.2 ounces, what proportion of the packages weigh less than the labeled amount? (Points : 1)

Question 10.10. Suppose the weights of the contents of cans of mixed nuts have a normal distribution with mean 32.6 ounces and standard deviation 0.4 ounce. 

 

If two packages are randomly selected, what is the probability that the average weight is less than 32 ounces? 

 

Round to one decimal place. (Points : 1)

Question 4.4. The city of Madison regularly checks the water quality at swimming beaches located on area lakes. The concentration of fecal coliforms, in number of colony forming units (CFU) per 100 ml of water, was measured each day for fifteen days during the summer at one beach. 

 180, 1600, 90, 140, 50, 260, 887 ,90, 380, 110, 12, 60, 20, 340, 80.





With reference to the given data, find the sample 90th percentile. (Points : 1)

       180

       19

       60

       20

       380

       180

       340

       887