How to find the quartiles for a set of...

Obtain a normal distribution table or calculator for this problem.

Approximate the $\small 90^{th}$ -percentile on the standard normal distribution.

$\small 1.28$

$\small 2$

$\small 1$

$\small 1.65$

Explanation

The $\small 90^{th}$ -percentile is the value such that $\small 90$ percent of values are less than it.

Using a normal table or calculator (such as R, using the command qnorm(0.9)), we get that the approximate $\small 90^{th}$ -percentile is about $\small 1.28$ .

Find the first and third quartile for the set of data

Explanation

In order to find the first and third quartiles, we haave to find the 25th and 75th percentiles, respectively.

To find the $n^{th}$ percentile, we find the product of and the number of items in the set.

We then round that number up if it is not a whole number, and the $p^{th}$ term in the set is the $n^{th}$ percentile.

For this problem, to find the $25^{th}$ and $75^{th}$ percentile, we first find that there are 14 items in the set. We find their respective products to be

$p_{25}=0.25*14=3.5\approx4$ and

$p_{75}=0.75*14=10.5\approx11$

As such, the $25^{th}$ and $75^{th}$ percentiles are the fourth and eleventh terms in the set, or

How to find the quartiles for a set of data

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