Quiz 7
1. Given that X ~ N(300, 15), we survey 20 at a time and are interested in the distribution of X-bar. As the number of data values averaged together gets larger, what happens to the standard error of the mean (the standard deviation of X-bar)?
a. It becomes larger.
b. It becomes smaller.
c. It approaches the average of X-bar.
d. It approaches the standard deviation of X.
2. Given X ~ Exp(1/8), we survey 100 at a time and are interested in the distribution of X-bar. Find the standard deviation of X-bar.
a. 0.8
b. 0.0125
c. 0.0800
d. 0.125
3. Given X ~ Exp(1/8), we survey 100 at a time and are interested in the distribution of X-bar. Find the third quartile of X-bar.
a. 6
b. 0.6321
c. 8.54
d. 2.30
4. Given that X ~ N(300, 15), we survey 20 at a time and are interested in the distribution of X-bar. Find the 33rd percentile of the distribution for X-bar.
a. 298.6
b. 293.5
c. 301.4
d. 100.0
5. Given that X ~ N(300, 15), we survey 20 at a time and are interested in the distribution of X-bar. Find the z-score associated with x-bar = 290.
a. -10/15
b. -10
c. -2.9814
d. -13.3333
6. Given X ~ Exp(0.125), we survey 100 at a time and are interested in the distribution of X-bar. P(X-bar < 7)=
____________.
a. 0.1056
b. 0.5831
c. 0.9987
d. 0.0001
7. Given X ~ U(2,18), we survey forty at a time and are interested in the distribution of X-bar. The standard deviation of X-bar is
a. 1.5811
b. 0.1155
c. 0.7303
d. 4.62
8. Given X ~ U(2,18), we survey forty at a time and are interested in the distribution of X-bar. P(X < 4) is ______ P(X-bar < 4).
a. less than
b. equal to
c. greater than
d. at most
9. Given X ~ U(2,18), we survey forty at a time and are interested in the distribution of X-bar. P(2 < X < 18) is _______ P(2 < X-bar < 18)
a. less than
b. equal to
c. greater than
d. at most
10. Given that X ~ N(300, 15), we survey 20 at a time and are interested in the distribution of X-bar. What can be said about the median of the random variable X-bar?
a. It is the same as the median of X.
b. It is the same as the average of X-bar.
c. It is the same as the average of X.
d. a, b, c are all correct.
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