# R notes for Activity 9-3: Value of Statistics

Although the book tells you that the data are stored in a single file, I've found it easier to segment it into five files, `ClassF`, `ClassG`, `ClassH`, `ClassI`, and `ClassJ`. You should load each separately. For example,

```ClassF = read.csv("/home/rebelsky/Stats115/Data/ClassF.csv")
```

Each of these CSV files contains a single column, titled `Ratings`. Hence, to make a histogram for one of them, you would write something like the following.

```hist(ClassF\$Ratings)
```

Of course, the book doesn't tell you to make your own histograms, but you might find it useful to do so.

What the book does is ask you to compute a variety of numbers, including range, interquartile range, and standard deviation. R's `range` function gives you the min and the max, rather the difference between the two. To compute the difference between the two, you need to subtract the max from the min.

```max(ClassF\$Ratings) - min(ClassF\$Ratings)
```

You compute interquartile range with `IQR` and standard deviation with `sd`. (And no, I do not know why they use different capitalization in different places.)

```IQR(ClassF\$Ratings)
sd(ClassF\$Ratings)
```

Problems i and j ask you to create a hypothetical example. Use something like the following (replacing the 0's by other numbers).

```iHypotheticals = c(0,0,0,0,0,0,0,0,0,0)
sd(iHypotheticals)
jHypotheticals = c(0,0,0,0,0,0,0,0,0,0)
sd(jHypotheticals)
```

Samuel A. Rebelsky, rebelsky@grinnell.edu

Copyright (c) 2007-8 Samuel A. Rebelsky.

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