Answer:
So the answer for this case would be n=2663 rounded up to the nearest integer
Step-by-step explanation:
We have the following info:
margin of error desired
the standard deviation for this case
The margin of error is given by this formula:
(a)
And on this case we have that ME =50 and we are interested in order to find the value of n, if we solve n from equation (a) we got:
(b)
The critical value for 99% of confidence interval now can be founded using the normal distribution. The significance is
. And for this case would be
, replacing into formula (b) we got:
So the answer for this case would be n=2663 rounded up to the nearest integer
Answer: 2:1
Step-by-step explanation:
The ratio of A to B is given by :
or A : B .
Given : sundaes with nuts = 4
sundaes without nuts = 8
The ratio of the number of sundaes with nuts to the number of sundaes without nuts = ![\dfrac{8}{4}=\dfrac{2}{1}\ \ \ [\text{Divide numerator and denominator by 4 }]](https://tex.z-dn.net/?f=%5Cdfrac%7B8%7D%7B4%7D%3D%5Cdfrac%7B2%7D%7B1%7D%5C%20%5C%20%5C%20%5B%5Ctext%7BDivide%20numerator%20and%20denominator%20by%204%20%7D%5D)
= 2:1
hence, the required ratio = 2:1 .
Answer:
a) 0.2416
b) 0.4172
c) 0.0253
Step-by-step explanation:
Since the result of the test should be independent of the time , then the that the test number of times that test proves correct is independent of the days the river is correct .
denoting event a A=the test proves correct and B=the river is polluted
a) the test indicates pollution when
- the river is polluted and the test is correct
- the river is not polluted and the test fails
then
P(test indicates pollution)= P(A)*P(B)+ (1-P(A))*(1-P(B)) = 0.12*0.84+0.88*0.16 = 0.2416
b) according to Bayes
P(A∩B)= P(A/B)*P(B) → P(A/B)=P(A∩B)/P(B)
then
P(pollution exists/test indicates pollution)=P(A∩B)/P(B) = 0.84*0.12 / 0.2416 = 0.4172
c) since
P(test indicates no pollution)= P(A)*(1-P(B))+ (1-P(A))*P(B) = 0.84*0.88+ 0.16*0.12 = 0.7584
the rate of false positives is
P(river is polluted/test indicates no pollution) = 0.12*0.16 / 0.7584 = 0.0253