Question

# 15. Random samples of size 81 are taken from an infinite population whose mean and standard...

15. Random samples of size 81 are taken from an infinite population whose mean and standard deviation are 200 and 18, respectively. The distribution of the population is unknown. The mean and the standard error of the mean are (assuming infinite population)

a. 200 and 18

b. 81 and 18

c. 9 and 2

d. 200 and 2

16. A population has a mean of 300 and a standard deviation of 18. A sample of 144 observations will be taken. The probability that the sample mean will be between 297 to 303 is (assuming infinite population)

a. 0.4332

b. 0.8664

c. 0.9544

d. 0.0668

17. Doubling the size of the sample will

a. reduce the standard error of the mean to one-half its current value

b. reduce the standard error of the mean to approximately 70% of its current value

c. have no effect on the standard error of the mean

d. double the standard error of the mean

18. A finite population correction factor is needed in computing the standard deviation of the sampling distribution of sample means

a. whenever the population is infinite

b. whenever the sample size is more than 5% of the population size

c. whenever the sample size is less than 5% of the population size

d. The correction factor is not necessary if the population has a normal distribution

In a local university, 40% of the students live in the dormitories. A random sample of 80 students is selected for a particular study. (assuming infinite population)

19. The standard deviation of , known as the standard error of the proportion is approximately

a. 0.5477

b. 5.477

c. 0.05477

d. 54.77

20. Refer to the information in Q19. The probability that the sample proportion (the proportion living in the dormitories) is between 0.30 and 0.50 is

a. 0.4664

b. 0.9328

c. 0.0336

d. 0.0672   