Can someone please help me i cant fail this

It is known that the life of a particular auto transmission follows a normal distribution with mean 72,000 miles and standard de

scoray [572]

Answer:

a) $P(X$

$P(z$

b) $P(X>65000)=P(\frac{X-\mu}{\sigma}>\frac{65000-\mu}{\sigma})=P(Z>\frac{65000-72000}{12000})=P(z>-0.583)$

$P(z>-0.583)=1-P(Z$

c) $P(X>100000)=P(\frac{X-\mu}{\sigma}>\frac{100000-\mu}{\sigma})=P(Z>\frac{100000-72000}{12000})=P(z>2.33)$

$P(z>2.33)=1-P(Z$

Sicne this probability just represent 1% of the data we can consider this value as unusual.

d) $z=1.28$

And if we solve for a we got

$a=72000 +1.28*12000=87360$

So the value of height that separates the bottom 90% of data from the top 10% is 87360.

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 life of a particular auto transmission of a population, and for this case we know the distribution for X is given by:

$X \sim N(72000,12000)$

Where $\mu=72000$ and $\sigma=12000$

We are interested on this probability

$P(X$

And the best way to solve this problem is using the normal standard distribution and the z score given by:

$z=\frac{x-\mu}{\sigma}$

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

$P(X$

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

$P(z$

Part b

$P(X>65000)$

And the best way to solve this problem is using the normal standard distribution and the z score given by:

$z=\frac{x-\mu}{\sigma}$

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

$P(X>65000)=P(\frac{X-\mu}{\sigma}>\frac{65000-\mu}{\sigma})=P(Z>\frac{65000-72000}{12000})=P(z>-0.583)$

And we can find this probability using the complement rule and excel or the normal standard table and we got:

$P(z>-0.583)=1-P(Z$

Part c

$P(X>100000)$

And the best way to solve this problem is using the normal standard distribution and the z score given by:

$z=\frac{x-\mu}{\sigma}$

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

$P(X>100000)=P(\frac{X-\mu}{\sigma}>\frac{100000-\mu}{\sigma})=P(Z>\frac{100000-72000}{12000})=P(z>2.33)$

And we can find this probability using the complement rule and excel or the normal standard table and we got:

$P(z>2.33)=1-P(Z$

Sicne this probability just represent 1% of the data we can consider this value as unusual.

Part d

For this part we want to find a value a, such that we satisfy this condition:

$P(X>a)=0.1$ (a)

$P(X$ (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 0.9 of the area on the left and 0.1 of the area on the right it's z=1.28. On this case P(Z<1.28)=0.9 and P(z>1.28)=0.1

If we use condition (b) from previous we have this:

$P(X$

$P(z$

But we know which value of z satisfy the previous equation so then we can do this:

$z=1.28$

And if we solve for a we got

$a=72000 +1.28*12000=87360$

So the value of height that separates the bottom 90% of data from the top 10% is 87360.

5 0

3 years ago

The SAT Reasoning Test (formerly called the Scholastic Aptitude Test) is perhaps the most widely used standardized test for coll

mihalych1998 [28]

Given Information:

Mean SAT score = μ = 1500

Standard deviation of SAT score = σ = 3 00

Required Information:

Minimum score in the top 10% of this test that qualifies for the scholarship = ?

Answer:

$\bar{x} = 1884\\$

Step-by-step explanation:

What is Normal Distribution?

We are given a Normal Distribution, which is a continuous probability distribution and is symmetrical around the mean. The shape of this distribution is like a bell curve and most of the data is clustered around the mean. The area under this bell shaped curve represents the probability.

We want to find out the minimum score that qualifies for the scholarship by scoring in the top 10% of this test.

$P(X > \bar{x} )= P(Z > \bar{x}) = 0.10\\P(X < \bar{x} )= P(Z < \bar{x}) = 1 - 0.10\\P(X < \bar{x} )= P(Z < \bar{x}) = 0.90\\$

The z-score corresponding to the probability of 0.90 is 1.28 (from the z-table)

$\bar{x} = \mu + z(\sigma) \\\bar{x} = 1500 + 1.28(300)\\\bar{x} = 1500 + 384\\\bar{x} = 1884\\$

Therefore, you need to score 1884 in order to qualify for the scholarship.

How to use z-table?

Step 1:

In the z-table, find the probability value of 0.90 and note down the value of the that row which is 1.2

Step 2:

Then look up at the top of z-table and note down the value of the that column which is 0.08

Step 3:

Finally, note down the intersection of step 1 and step 2 which is 1.28

4 0

3 years ago

Which is enough information to prove that s is parallel to t? Lines s and t are cut by transversal r to form 8 angles. Clockwise

serg [7]

Answer:The answer is B

Step-by-step explanation:

3 0

3 years ago

Read 2 more answers

What is 6(7-2p) =12p+42

mafiozo [28]

answer:

p = 0

step-by-step explanation:

6 (7-2p) = 12p + 42

42 - 12p = 12p + 42

+12p +12p

_______________

42 = 24p + 42

-42 -42

_____________

0 = 24p

_ ___

24 24

0 = p

<em>hope this helps! ❤ from peachimin (aka kayla)</em>

4 0

3 years ago

Six friends will stay at a cabin in the woods this weekend. The distance to the cabin is 148.5 miles. Each person will drive one

ivolga24 [154]

Answer:

24.75/24¾

Step-by-step explanation:

148.5 ÷ 6 = 24¾ or 24.75

Answer: Each driver drove 24.75/24¾ miles

5 0

3 years ago