A population of insects, in thousands, can be molded using the function (t)= 1.75(0.97)x
1 answer:
Question:
A population of insects, in thousands, can be modeled using the function
, where t is time in months. Which statement best
describes the population of insects?
A. The population is decaying at a rate of 3% each month.
B. The population is decaying at a rate of 25% each month.
C. The population is growing at a rate of 75% each month.
D. The population is growing at a rate of 97% each month.
Answer:
A. The population is decaying at a rate of 3% each month.
Step-by-step explanation:
Given
Required
True statement about the function
From the options, we can see that we are to answer the question on the basis of decay and growing rates.
An exponential form is:
Compare to
If , then
r represents growth rate
else, r represents decay rate
Since b < 0.97:
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Answer:
And if we solve for a we got;
So the value of height that separates the bottom 95% of data from the top 5% is 11.64
Step-by-step explanation:
Previous concepts
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".
The Z-score is "a numerical measurement used in statistics of a value's relationship to the mean (average) of a group of values, measured in terms of standard deviations from the mean".
Solution to the problem
Let X the random variable that represent certain lifetime of a population, and for this case we know the distribution for X is given by:
Where and
For this part we want to find a value a, such that we satisfy this condition:
(a)
(b)
Both conditions are equivalent on this case. We can use the z score again in order to find the value a.
As we can see on the figure attached the z value that satisfy the condition with 0.95 of the area on the left and 0.05 of the area on the right it's z=1.64. On this case P(Z<1.64)=0.95 and P(z>1.64)=0.05
If we use condition (b) from previous we have this:
But we know which value of z satisfy the previous equation so then we can do this:
And if we solve for a we got;
So the value of height that separates the bottom 95% of data from the top 5% is 11.64