Hello, I need some help. There is a file attached. This should be done with quality!

Periwinkle Shell Variability – Descriptive Statistics & Histograms (10 pts)

The periwinkle is a small (ca. 1 cm long) marine snail that lives in the intertidal zone in New England. In 1982 and 1983 biologist Robin Seeley collected and measured shells of snails she collected in the Cape Cod area. She also measured museum specimens collected pre-1900 Cod. Her data are given in Table 1.

Table 1. Shell thickness, in millimeters, of periwinkles collected near Cape Cod, MA. Shell thickness was measured with a caliper. Snails were collected directly from the littoral zone in 1982 and 1983. Data from pre-1900 were obtained from snails in museum collections.
Sample #	Pre-1900	1982-1983
		14

	11	14
		14
		15
		11
		11
		10
		12
10	13	13
11		12
12		12
13		14
14		13
15		14
16		14
17		13
18		10
19		10
20	10	15
21		12
22		13
23	11	15
24	12	16
25		17
26		16
27		12
28		18
29		16
30		15
31		15
32		13
33		15
34		11
35		17
Mean

Descriptive Statistics: We can use a variety of statistics to summarize our data including range, mean (average), and median. Complete the following data table.

Table 2. Summary of descriptive statistics comparing shell thickness (in millimeters) of periwinkles collected prior to 1900 and during 1982 & 1983.
Statistic	Pre-1900	1982-1983

Range (mm)
Median (mm)
Mean (mm)

Histograms: A particularly good way to represent variation in a population is to use a histogram or frequency distribution which plots number of observations in a given category vs. category. Perhaps the biggest trick in creating a histogram is selecting the size of the categories (bins) – too few or too many will provide less information. In this case, we will make it simple by creating a histogram with bins of 2mm increments. Complete Table 3 by adding up the number of observations in each of the categories for each population.

Table 3. Frequency distribution of shell thickness for periwinkles collected pre-1900 and in 1982-1983 near Cape Cod, MA.
Shell Thickness Category (mm)	Number of Observations
Pre-1900	1982-1983
0 – 1.9
2.0 – 3.9
4.0 – 5.9
6.0 – 7.9
8.0 – 9.9
10.0 – 11.9
12.0 – 13.9
14.0 – 15.9
16.0 – 17.9
18 – 19.9

Now,

label the Y axis “number of observations” and
label the X axis appropriately.
Then plot the data. Darken in the bars for each. The figure should have an appropriate figure legend underneath the figure with figure number and an indication of what this graph shows, with appropriate units.

Summary Question:

What conclusions about the periwinkles do you draw from the graphs?

Pre - 1900 population

1982-3 population