# stat 540 question

Point values are shown in parentheses; 35 points total

1. (10 points). The data set XYdata.csv posted on Bb were collected in petri dishes, with each

dish having a given concentration of Cadmium Chloride (X, micrograms/liter) in solution, and

the growth of algae cells Y (cells x 10^4/ml) in the was dish recorded after two weeks’ time.

Input the data into R, creating a data frame. Provide me the commands you used and issue ls()

to check that it’s there. Then construct a scatter plot of the data (X on the horizontal axis), with

a title and well-labeled axes (include units of measurement somewhere on the plot). Include

your name in the title. Then, add a smooth fitted quadratic curve given by the equation

126.760+(-4.47126)*x+(0.0369577)*x2

Make sure that all the points and the entire curve fit on the plot. Provide me the commands

you used to construct your final graph, as well the graph itself.

2. (10 points) The Statistics department’s distance-ed headcount enrollments by term (three

terms per year – FA, SP, SU etc.) from Fall 1999 through Fall 2004 were:

2, 1, 0, 4, 10, 3, 9, 8, 0, 9, 10, 6, 20, 23, 8, 23.

Get this data into R as a numeric vector (type it carefully using c()). Then, use the data to

construct a graph like the one at the top of the next page, except include your name in the title.

Hint: look for the names.arg argument in help(barplot). Also, look at help(legend) to place the

text in a box at top left in the graph. Give me the commands you used and the graph itself. The

color need not match exactly, but the legend should be two lines at top left of the graph.

STAT 540 Hwk 2 p.1

3. (15 points) Issue the command >data(WorldPhones) and then inspect the loaded data. Then,

construct a graph as similar to the one shown below as you can; use your name in the title.

Provide me the commands you used and the graph itself. Hint: under help(lines), look for the

option type. Also, see help(legend). Note that the plot starts in 1956, though the first row of

the raw data is 1951.

STAT 540 Hwk 2 p.2

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