2 histograms, the first titled 1970 and the second titled 2015. The Y-axis of each histogram is labeled Number of Cactuses, and the X-axis is labeled Spine Size in intervals from 1 to 10, with 1 labeled Small and 10 labeled Large. The height of the bars in the first histogram ascends and descends evenly from 2 to 9, peaking at 5 and 6, with no bars at 1 and 10. The height of the bars in the second histogram also ascends and descends evenly from 2 to 9, peaking at 5 and 6, but about half as high as the first histogram.

Question

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9. Scientists measured the spine size of a population of cactuses found in an area in 1970. They measured the spine size of the cactus population again in 2015. Which of the statements below best describes the difference in the cactuses at the two time points?
Responses

a
The cactuses in 1970 had smaller spines than the cactuses in 2015.
The cactuses in 1970 had smaller spines than the cactuses in 2015.

b
The cactuses in 1970 had larger spines than the cactuses in 2015.
The cactuses in 1970 had larger spines than the cactuses in 2015.

c
There were more cactuses in 1970 than there were in 2015.
There were more cactuses in 1970 than there were in 2015.

d
There was more variation in spine size in 1970 than there was in 2015.

Answer 1

Based on the description of the histograms, the best statement that describes the difference in the cactuses at the two time points is:

b: The cactuses in 1970 had larger spines than the cactuses in 2015.

This conclusion is drawn from the observation that the heights of the bars in the first histogram (1970) are higher, indicating a larger population of cactuses with larger spine sizes compared to the second histogram (2015), which shows a decrease in both the number of cactuses and their spine sizes.