Download TFV0103 Tölfræði og fræðileg vinnubrögð Heimavinna 8 1

TFV0103 Tölfræði og fræðileg vinnubrögð Heimavinna 8
Kafli 8
1. If n = 150, x-bar (sample mean) = 225,
sigma (staðalfrávik) = 50, what is the 95%
confidence interval (öryggisbil) for the
population mean (mu) ?
6. For the sample (114, 120, 108, 118, 119,
123, 117, 124, 115, 129), what is x-bar
(meðaltal) ?
a) 115,7
b) 116,7
c) 117,7
d) 118,7
a) [217 to 233]
b) [175 to 275]
c) [200 to 250}
d) [210 to 240]
7. For the sample (114, 120, 108, 118, 119,
123, 117, 124, 115, 129), what is the 95%
confidence interval (öryggisbil) for the
population mean if sigma (staðalfrávik) = 6,1 ?
2. If n = 100, x-bar (sample mean) = 40,6,
sigma (staðalfrávik) = 5, what is the 95%
confidence interval (öryggisbil) for the
population mean (mu) ?
a) [118,00 to 119,40]
b) [114,92 to 122,48]
c) [112,60 to 124,80]
d) [113,70 to 123,70]
a) [35,6 to 45,6]
b) [39,6 to 41,6]
c) [30,6 to 50,6]
d) [38,1 to 43,1]
8. For the sample (114, 120, 108, 118, 119,
123, 117, 124, 115, 129), what is the 99%
confidence interval (öryggisbil) for the
population mean if sigma (staðalfrávik) = 6,1 ?
3. If n = 18, x-bar (sample mean) = 9,87, sigma
(staðalfrávik) = 0,27, what is the 95%
confidence interval (öryggisbil) for the
population mean (mu) ?
a) [113,5 to 123,5]
b) [113,7 to 123,7]
c) [113,9 to 123,9]
d) [118,5 to 118,9]
a) [9,60 to 10,14]
b) [9,07 to 10,67]
c) [9,75 to 9,99]
d) [9,85 to 9,89]
4. If n = 60, x-bar (sample mean) = 65,5, sigma
(staðalfrávik) = 2,5, what is the value in the
middle of the 95% confidence interval
(öryggisbil) for the population mean ?
9. For a 95% confidence interval (öryggisbil)
the multiplier is 1,96. For the 99% confidence
interval the multiplier is 2,575. What
multiplier is used for a 99,9% confidence
interval (BOOKTABLE3) ?
a) 60
b) 65,5
c) 2,5
d) 30
a) 1,29
b) 2,29
c) 3,29
d) 4,29
5. If a 95% confidence interval for a
population mean is [44,8 to 50,2], what was
the x-bar (sample mean) used to calculate the
confidence interval ?
10. For the sample (114, 120, 108, 118, 119,
123, 117, 124, 115, 129), what is the 99,9%
confidence interval (öryggisbil) for the
population mean if sigma (staðalfrávik) = 6,1 ?
a) 44,8
b) 50,2
c) 47,5
d) 46,5
a) [115,52 to 121,88]
b) [114,92 to 122,48]
c) [113,7 to 123,7]
d) [112,35 to 125,05]
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TFV0103 Tölfræði og fræðileg vinnubrögð Heimavinna 8
11. If you took 100 samples (úrtak) from a
population (þýði) and constructed 100 95%
confidence intervals (öryggisbil), how many of
the 100 confidence intervals would you expect
to contain the population mean?
16. In a statistical test, the alpha level is 0,05
and the p-value is 0,08. Which statement is
true?
a) The null hypothesis should be accepted.
b) The null hypothesis should be rejected.
c) The alpha level should be 0,10.
d) The p-value must be written using 8 decimal
places (aukastafar).
a) 100
b) 99
c) 95
d) 90
17. If the sample size is 35 (n=35), x-bar (the
sample mean) is 63,5, and sigma (staðalfrávik)
is 2,5. What is z* (the test statistic), if the
population mean is stated to be 65?
12. If you took 100 samples (úrtak) from a
population (þýði) and constructed 100 99%
confidence intervals (öryggisbil), how many of
the 100 confidence intervals would you expect
to contain the population mean?
a) -3,55
b) +3,55
c) -2,5
d) +2,5
a) 100
b) 99
c) 95
d) 90
18. If the sample size is 35 (n=35), x-bar (the
sample mean) is 63,5, sigma (staðalfrávik) is
2,5, and the population mean is stated to be 65,
what is the probability p(z<z*)
(BOOKTABLE3) where z* is the test statistic.
13. If you are testing the difference between
drug X and drug Y, what is the null hypothesis
(núlltilgáta) ?
a) Drug X is faster than drug Y.
b) Drug Y is faster than drug X.
c) There is no difference between drug X and
drug Y.
d) There is a difference between drug X and
drug Y.
a) 0,2
b) 0,02
c) 0,002
d) 0,0002
19. If the sample size is 35 (n=35), x-bar (the
sample mean) is 63,5, sigma (staðalfrávik) is
2,5, the alpha level is 0,01, and the null
hypothesis is that the population mean >= 65,
which statement is true ?
14. If you are testing the difference between a
new drug X and an old drug Y, what is the
alternative hypothesis (hin tilgáta) ?
a) Drug X is faster than drug Y.
b) Drug X is as slow as drug Y.
c) There is no difference between drug X and
drug Y.
d) There is a difference between drug X and
drug Y.
a) The alternative hypothesis should be
accepted.
b) The null hypothesis should be accepted.
c) The alpha level is too small.
d) The alpha level is too high.
20. Which statement is true about the
calculations performed for Questions 17, 18,
and 19.
15. In a statistical test, the alpha level is 0,05
and the p-value is 0,02. Which statement is
true?
a) The calculations were for a one-tailed (left
tail) test.
b) The calculations were for a one-tailed (right
tail) test.
c) The calculations were for a two-tailed test.
d) The calculations were for a three-tailed test.
a) The null hypothesis should be accepted.
b) The null hypothesis should be rejected.
c) The alpha level should be 0,10.
d) The p-value must be written using 8 decimal
places (aukastafar).
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