The compressive strength of samples of cement can be modeled by a normal distribution with a mean of 6,098 kilograms per square centimeter and a standard deviation of 103 kilograms per square centimeter. Determine the probability a sample's strength is exactly 6,076 kilograms per centimeter squared. Round your answer to two decimal places.

Respuesta :

Answer:

By definition [tex] P(X= 6076)=0[/tex] since in a continuous probability distribution the area below a line is 0

If the real question is:

[tex] P(X<6076)[/tex]

We can use the z score formula given by:

[tex]z=\frac{x-\mu}{\sigma}[/tex]

If we apply this formula to our probability we got this:

[tex]P(X<6076)=P(\frac{X-\mu}{\sigma}<\frac{6076-\mu}{\sigma})=P(Z<\frac{6076-6098}{103})=P(z<-0.214)[/tex]

And we can find this probability using the normal standard table or excel:

[tex]P(z<-0.214)=0.415[/tex]

And if the question is [tex] P(X>6076)[/tex] we apply the complement rule and we got:

[tex] P(X>6076) = 1-P(X<6076) = 1-0.415=0.585[/tex]

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 the strengths of a population, and for this case we know the distribution for X is given by:

[tex]X \sim N(6098,103)[/tex]  

Where [tex]\mu=6098[/tex] and [tex]\sigma=103[/tex]

For this case we want [tex] P(X= 6076) [/tex]

And by definition [tex] P(X= 6076)=0[/tex] since in a continuous probability distribution the area below a line is 0

If the real question is:

[tex] P(X<6076)[/tex]

We can use the z score formula given by:

[tex]z=\frac{x-\mu}{\sigma}[/tex]

If we apply this formula to our probability we got this:

[tex]P(X<6076)=P(\frac{X-\mu}{\sigma}<\frac{6076-\mu}{\sigma})=P(Z<\frac{6076-6098}{103})=P(z<-0.214)[/tex]

And we can find this probability using the normal standard table or excel:

[tex]P(z<-0.214)=0.415[/tex]

And if the question is [tex] P(X>6076)[/tex] we apply the complement rule and we got:

[tex] P(X>6076) = 1-P(X<6076) = 1-0.415=0.585[/tex]