Suppose the heights of women at a college are approximately Normally distributed with a mean of 66 inches and a population standard deviation of 1.5 inches. What height is at the 10 th percentile? Include an appropriately labeled sketch of the Normal curve to support your answer.

And if we solve for a we got

So the value of height that separates the bottom 10% of data from the top 90% is 64.08.

The graph attached illustrate the situation.

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 heights 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 0.10 of the area on the left and 0.90 of the area on the right it's z=-1.28. 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 10% of data from the top 90% is 64.08.

The graph attached illustrate the situation.

e.

step-by-step explanation:

because there are always 10 numbers in a phone number.

its kind of blurry. can you put a clearer pic?

step-by-step explanation: