Question

years of exposure
20 22 24 26 28 30 32 34
a geologist used beryllium - 10 dating on several samples of rock at a site to estimate how long the rock had been exposed at the surface. which of the following best compares the median to the mean of the data?
choose 1 answer:
a the median and the mean are approximately equal, because the distribution is symmetrical.
b the median is lower than the mean because 2 of the samples are several years older than the rest.
c the median is higher than the mean because many more of the samples had 25 years or less of exposure.
d there is not enough information to compare the median and the mean.

Explanation:

Step1: Analyze the data distribution visually

From the dot - plot, we can see that most of the data points are clustered on the lower - end (20 - 25 years of exposure), and there are two data points at the higher end (32 and 34 years of exposure). This is a right - skewed distribution.

Step2: Recall the property of mean and median in skewed distributions

In a right - skewed distribution, the mean is pulled in the direction of the tail (higher values). The median is the middle value when the data is ordered. Since the tail on the right side affects the mean but not the median as much, the median is lower than the mean.

Answer:

B. The median is lower than the mean because 2 of the samples are several years older than the rest.