http://www.ck12.org Chapter 1. An Introduction to Analyzing Statistical Data
FIGURE 1.
Lonesome George, the Last Pinta tor-
toise, Charles Darwin Research Station,
Santa Cruz, Galapagos Islands.(b) Researchers collect data over 15 years about 100 sets of identical twins to see how their personalities
develop similar or different characteristics.
(c) Cloned mice are put into different colored cage environments to see if there is an effect on their temper-
aments.
(d) Researchers find that babies who were exposed to lead paint have a high risk of brain damage.Review Answers
- Ordinal
- Nominal
- Interval. Even though Celsius has a “0”, this is a completely arbitrary decision to set the freezing point of
water and not the “absence” of temperature. - Ratio. The Kelvin scale is based on an absolute zero, the theoretical temperature at which molecules stop
moving. - The levels of measurement theory is a useful tool to help categorize data, but like much of statistics, it is not
an absolute “rule” that applies easily to every situation and several statisticians have pointed out some of the
difficulties with the theory. See: http://en.wikipedia.org/wiki/Level_of_measurement - Population densities are certainly measured up to the interval level as there is meaning to the values and
distance between two observations. To decide if it is measured at the ratio level, we need to establish a
meaning for absolute zero. In this case, it would be 0 individuals perkm^2. This is possible and indeed
represents the extinct populations. - This is an experiment as each subject is drinking both waters (the imposed treatment). However, it will have
to be designed properly. Students should not know which water is bottled and which is tap (this is called a
“blind” experiment) and they should be randomly assigned the order in which they drink the water. Other
conditions such as the appearance, amount, and temperature would also need to be tightly controlled.