D(t)D, left parenthesis, t, right parenthesis models the distance (in thousands of \text{km}kmstart text, k, m, end text) from t
he earth to the Moon ttt days after the moon's perigee (when it's closest to the earth). Here, ttt is entered in radians. D(t) = -21\cos\left(\dfrac{2\pi}{29.5}t\right) + 384D(t)=−21cos( 29.5 2π t)+384D, left parenthesis, t, right parenthesis, equals, minus, 21, cosine, left parenthesis, start fraction, 2, pi, divided by, 29, point, 5, end fraction, t, right parenthesis, plus, 384 How many days after its perigee does the moon first reach 380380380 thousands of \text{ km} kmstart text, space, k, m, end text from the Earth?
1 answer:
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Answer:
a) 0.2741 = 27.41% probability that at least 13 believe global warming is occurring
b) 0.7611 = 76.11% probability that at least 110 believe global warming is occurring
Step-by-step explanation:
Binomial probability distribution
The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.
In which is the number of different combinations of x objects from a set of n elements, given by the following formula.
And p is the probability of X happening.
The expected value of the binomial distribution is:
The standard deviation of the binomial distribution is:
Normal probability distribution
Problems of normally distributed samples can be solved using the z-score formula.
In a set with mean and standard deviation
, the zscore of a measure X is given by:
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the pvalue, we get the probability that the value of the measure is greater than X.
When we are approximating a binomial distribution to a normal one, we have that ,
.
In this problem, we have that:
(a) For a sample of 16 Americans, what is the probability that at least 13 believe global warming is occurring?
Here , we want
. So
In which
0.2741 = 27.41% probability that at least 13 believe global warming is occurring
(b) For a sample of 160 Americans, what is the probability that at least 110 believe global warming is occurring?
Now . So
Using continuity correction, this is , which is 1 subtracted by the pvalue of Z when X = 109.5. So
has a pvalue of 0.2389
1 - 0.2389 = 0.7611
0.7611 = 76.11% probability that at least 110 believe global warming is occurring