50
make a box and whisker plot of the data
see photo

Let's try it just using test taking skills first, without really knowing anything about what these plots are.

All have a minimum of 13 and a max of 29 so those don't help.

Three have a left box edge of 14.5, one 12.8 or so.  The correct answer is probably 14.5.

Three have a median of 19.5, one of 20.5, so 19.5 is probably right.

Similarly 23.5 is the most common right box edge.  

So we're looking for the plot with 13/14.5/19.5/23.5/29, which is the first choice.

Instead of Einsteining the test, lets review the material.  A box and whiskers plot shows the min and max (whisker ends), the 25th and 75th percentiles (box ends) and the 50th percentile, the median, which is the dot in the middle.

Let's start by sorting the 8 data points:

11 13 16 18 21 23 24 29

The minimum is 11 and the maximum is 29.  All the charts agree on this.

The median is the middle, which is the average of 18 and 21, so

median = 19.5

That rules out the one selected, it can't be the third one.

The 25th percentile basically the median of the first four numbers, so the average of 13 and 16,

25th percentile = 14.5

The 75th percentile is similarly the average of 23 and 24

75th percentile 23.5

Examining the choices we find our

first choice