An individual stock is selected at random from the portfolio represented by the box-and-whisker plot shown. Find the probability that the stock price is (a) less than $21, (b) between $21 and $50, and (c) $30 or more.

Solution :

Step 1 of 3:

Given the portfolio represented by the box-and-whisker plot is given below,

Our goal is:

a). We need to find the probability that the stock price less than 21.

b). We need to find the probability that the stock price between 21 and 50.

c). We need to find the probability that the stock price 30 or more.

a). From the above plot, the following information is

The minimum value is 12 and the percentile is 21.

The median (50th percentile) is 30

Then the maximum value is 94 and the 75th percentile is 50.

From the given information we know that to understand the data, this means 25% of the data is between the minimum and the percentile.

Then 25% of the data is between the percentile and median.

Now we have to find the probability less than 21.

So It's no coincidence that this is the percentile.

Here 25% of the data is below 21 so the probability is 25%.

Therefore, the probability that the stock price less than 21 is 25 percent.