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6) Suppose =36 and sample size n = 81. What is the standard error (S.E) of x ? S

ID: 2928164 • Letter: 6

Question

6) Suppose =36 and sample size n = 81. What is the standard error (S.E) of x ?

Select one:

a. 0.45

b. 4

c. 13.5

7) The sample proportion, p(bar) = 0.25 and n=36. At the 99% confidence level, the margin of error is computed to be 0.05. Which one of the following represents the 99% confidence interval estimate of p? Select one:

a. 0.25 ± 0.05

b. 0.25 ± 0.025

c. 0.25 ± 0.07

8) The sample proportion, p(bar) = 0.25 and n=36. The standard error of p(bar) (rounded to two decimal places) is given by Select one:

a. ((0.25*0.75)/36) = 0.07

b. 0.25/36 = 0.04

c. (0.25*0.75) = 0.43 9)

9) We have n=15, x =10, s=4 and (1-)=0.99. The standard error of x (rounded to two decimal places) is Select one:

a. 0.27

b. 1.03

c. 7.5

10)We have n=15, x(bar)=10, s=4 and (1-)=0.99. Using Excel and after rounding to two decimal places, the critical value, t/2, is Select one:

a. 2.98

b. 1.76

c. 2.14

11) When one increases the confidence level (1-), say from 0.90 to 0.95, Select one:

a. margin of error will increase

b. the resulting confidence interval will capture the population parameter more often

c. both A and B are correct

12) When the population standard deviation () is known and we wish to estimate , the margin of error is obtained as Select one:

a. z/2 × s/n

b. t/2 × s/n

c. z/2 × /n

13) When the population standard deviation () is NOT known and we wish to estimate , the margin of error is obtained as Select one:

a. z/2 × s/n

b. t/2 × s/n

c. z/2 × /n

14) Which one of the following is a point estimator? Select one:

a.

b. x (bar)

c. p

15) We have n=15, x(bar) =10, s=4, and (1-)=0.99. We wish to obtain the 99% confidence interval estimate of . What is the margin of error (rounded to two decimal places)?

Explanation / Answer

6)  standard error (S.E) of x = /(n)1/2 =4

option b. 4

7)

a. 0.25 ± 0.05

8)

standard error of p(bar)  

a. ((0.25*0.75)/36) = 0.07

9) standard error of x =s/(n)1/2

b. 1.03

10)critical value, t/2 =

a. 2.98

11)

c. both A and B are correct

12)

c. z/2 × /n

13)

b. t/2 × s/n

14)

b. x (bar)

15)

std error = s/n =1.03

for t =2.98

therefore margin of error =t*std error=3.07

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