A monsoon dumped rain on a coastal area. in twelve hours 20 inches of rain had fallen. how much rain will fall over a period of
2 answers:
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Answer:
1) n=48
2) n=298
3) n=426
Step-by-step explanation:
Previous concepts
A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".
The margin of error is the range of values below and above the sample statistic in a confidence interval.
Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".
represent the real population proportion of interest
represent the estimated proportion for the sample
n is the sample size required (variable of interest)
represent the critical value for the margin of error
The population proportion have the following distribution
Part 1
In order to find the critical value we need to take in count that we are finding the interval for a proportion, so on this case we need to use the z distribution. Since our interval is at 90% of confidence, our significance level would be given by and
. And the critical value would be given by:
The margin of error for the proportion interval is given by this formula:
(a)
And on this case we have that and we are interested in order to find the value of n, if we solve n from equation (a) we got:
(b)
We can assume that the estimated proportion is 0.23 for the 25 to 30 group. And replacing into equation (b) the values from part a we got:
And rounded up we have that n=48
Part 2
The margin of error on this case changes to 0.04 so if we use the same formula but changing the value for ME we got:
And rounded up we have that n=298
Part 3
In order to find the critical value we need to take in count that we are finding the interval for a proportion, so on this case we need to use the z distribution. Since our interval is at 95% of confidence, our significance level would be given by and
. And the critical value would be given by:
The margin of error for the proportion interval is given by this formula:
(a)
And on this case we have that and we are interested in order to find the value of n, if we solve n from equation (a) we got:
(b)
We can assume that the estimated proportion is 0.23 for the 25 to 30 group. And replacing into equation (b) the values from part a we got:
And rounded up we have that n=426
Answer:
0.2%
Step-by-step explanation:
The given parameters are;
The percentage of product within the correct range = 95%
The percentage of the times the sensor reject boxes of incorrect weight = 98%
The percentage of the times the company reject boxes with correct weight = 1%
We have, FN = 0.9, TN = 9.8, TP = 90 - 0.9 = 89.1, FP = 10 - 9.8 = 0.2
FNR = FN/(FN + TP) = 0.9/(0.9 + 89.1) = 0.01
FPR = 0.2/(0.2 + 9.8) = 0.02
TPR = 89.1/(89.1 + 0.9) = 0.99
TNR = 9.8/(9.8 + 0.2) = 0.98
P(C/A) = TPR × P(C)/((TPR × P(C) + FPR×(1 - P(C)))
Where;
P(C/A) = The probability that a correct weight package is accepted
∴ P(C/A) = 0.99*0.9/(0.99*0.9 + 0.02*0.1) ≈ 0.99776
The probability that a correctly weighed package is rejected, P(C/R), is given as follows;
P(C/R) = 1 - P(C/A)
∴ P(C/R) ≈ 1 - 0.99776 = 0.00224 ≈ 0.2%
The probability that a correctly weighed package is rejected, P(C/R) ≈ 0.2%