Paula is painting a henhouse. If a can of paint will cover 24 square feet, how many cans of paint does she need to buy? Explain
1 answer:
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Answer:
a)
And we can find this probability using the complement rule:
And in order to find these probabilities we can use tables for the normal standard distribution, excel or a calculator.
b)
And we can use the z score formula given by:
And in order to find these probabilities we can use tables for the normal standard distribution, excel or a calculator.
c)
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 0.7312.
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".
Part a
Let X the random variable that represent the substrate concentration of a population, and for this case we know the distribution for X is given by:
Where and
We are interested on this probability
And the best way to solve this problem is using the normal standard distribution and the z score given by:
If we apply this formula to our probability we got this:
And we can find this probability using the complement rule:
And in order to find these probabilities we can use tables for the normal standard distribution, excel or a calculator.
Part b
And we can use the z score formula given by:
And in order to find these probabilities we can use tables for the normal standard distribution, excel or a calculator.
Part c
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 0.7312.