Suppose you were a veterinarian responsible for the health of the animals in a laboratory colony. One very important clue to health in any animal (including humans) is
body weight. To help you maintain the health of the animals in your care, you need to
know what a typical laboratory animal weighs (in this example, the albino SpragueDawley lab rat, which is very commonly used for lab research because they are calm
and easy to handle). The body weights for a set of 30 adult, albino Sprague-Dawley laboratory rats (15 males and 15 females) are shown in Table 5.8. Find the mean, median,
mode, range, variance, and standard deviation for this set of animals.
$$
\begin{array}{c|c}
\hline \text { Females } & \text { Males } \\
\hline 229 & 510 \\
\hline 300 & 485 \\
\hline 310 & 476 \\
\hline 248 & 528 \\
\hline 304 & 448 \\
\hline 286 & 498 \\
\hline
\end{array}
$$
$$
\begin{array}{|l|l|}
\hline 291 & 468 \\
\hline 284 & 575 \\
\hline 291 & 489 \\
\hline 279 & 529 \\
\hline 289 & 411 \\
\hline 285 & 453 \\
\hline 247 & 518 \\
\hline 282 & 441 \\
\hline 248 & 466 \\
\hline
\end{array}
$$
Once you’ve found these statistics (our measure of typical), answer the following
questions:
a. In your newest shipment of rats, they’ve forgotten to tell you the sex of each animal,
and all you have to go on are the body weights shown in the chart below. Using only
the body weights provided, determine if the animals are probably male or probably
female.
b. Were there any rats that you were unable to make a prediction for? If so, why did
you have difficulty?
c. Now that we know what “typical” is, speculate how you might determine what atypical would be. How far away from the mean would an unhealthy animal (too fat or
too thin) be?
$$
\begin{array}{c|c|c|c}
\hline \begin{array}{c}
\text { Body Weight (in } \\
\text { Grams) }
\end{array} & \begin{array}{c}
\text { Check Here if Rat is } \\
\text { Probably FEMALE }
\end{array} & \begin{array}{c}
\text { Check Here if Rat is } \\
\text { Probably MALE }
\end{array} & \begin{array}{c}
\text { Check Here if you can't make a } \\
\text { Prediction About the Sex of the Animal } \\
\text { Based on Body Weight Alone }
\end{array} \\
\hline 249 & & & \\
\hline 500 & & & \\
\hline 390 & & & \\
\hline 400 & & & \\
\hline 290 & & & \\
\hline
\end{array}
$$