Zou iemand wellicht mijn antwoorden willen checken of ze correct zijn?
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KLM.TXT
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Code: Selecteer alles
70.00
59.00
28.00
59.00
33.00
48.00
84.00
20.00
64.00
23.00
29.00
72.00
37.00
30.00
30.00
52.00
40.00
177.00
54.00
214.00
167.00
70.00
55.00
76.00
29.00
46.00
75.00
74.00
57.00
56.00
32.00
21.00
22.00
18.00
39.00
126.00
103.00
303.00
7.00
38.00
26.00
44.00
32.00
80.00
29.00
77.00
65.00
77.00
36.00
65.00
6.00
32.00
37.00
25.00
30.00
31.00
23.00
56.00
29.00
27.00
A)
Assume that the measurements indeed form a sample from the distribution that
you chose in part c. Estimate based this assumption and with the use of R the
following probabilities:
i) the probability that the delivery time is smaller than 50;
ii) the probability that the delivery time is larger than 150;
iii) the probability that the delivery time is between 10 and 200.
B)
Compare the estimates of part A) with the estimates for the same probabilities that you would obtain if you would use the relative frequency based on the delivery time data for estimating the probabilities.
C)
Does the comparison of part B) tell you anything about the plausibility of the assumption used in part A)?
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Mijn antwoorden:
A)
(i) The probability that the delivery time is smaller than 50 is 0.288424.
Code: Selecteer alles
> mean(xpop)
[1] 57.73333
> mean(xsamp)
[1] 29.60606
> sd(xpop)
[1] 50.40778
> (mean(xsamp) - mean(xpop)) / sd(xpop)
[1] -0.5579946
> pnorm(-0.5579946)
[1] 0.288424
Code: Selecteer alles
> mean(xpop)
[1] 57.73333
> mean(xsamp)
[1] 215.25
> sd(xpop)
[1] 50.40778
> (mean(xsamp) - mean(xpop)) / sd(xpop)
[1] 3.124848
> 1 - pnorm(3.124848)
[1] 0.0008894848
Code: Selecteer alles
> mean(xpop)
[1] 57.73333
> mean(xsamp)
[1] 52.39286
> sd(xpop)
[1] 50.40778
> (mean(xsamp) - mean(xpop)) / sd(xpop)
[1] -0.1059455
> 2*pnorm(-0.1059455)
[1] 0.9156256
(i) Based on the relative frequency, the probability that the delivery time is smaller than 50 is 0.55.
(ii) Based on the relative frequency, the probability that the delivery time is larger than 150 is 0.06667.
(iii) Based on the relative frequency, the probability that the delivery time is between 10 and 200 is 0.93333.
C)
The results of part A and B are different. There are not enough samples of the delivery time. Both the sample mean and the populations mean dont have the same standard deviation. They even dont have the same z-score and the same probability.
MVG