ch02 characteristic of scores

The characteristics of scores

always pay attention to two important characteristics of the variables:
the type of measurement scale involved
and wether
the scale is continuous or discrete.

** The four types of measurement scales
Numbers mean different things in different contexts.
* nominal scale, each score does not actually indicate an amount; rather, it is used for identification.
* A different approach is to use an ordinal scale.Here the scores indicate rank order--anything that is akin to 1st, 2nd, 3rd... is ordinal.
relatively high or low Also, there is no zero in ranks
* interval scale.Indicate an actual quantity, and an equal amount separates any adjacent scores.(equal intervals between them --histogram--)
* ratio scale, the scores reflect the true amount of the variable that is present.

** Continuous versus Discrete Scales
Note: when a discrete variable has only two possible categories or scores, it is called a dichotomous variable. Male/female or living/dead are dichotomous variables.

REMEMBER: Whether a variable is continuous or discrete and wether it is measured using a nominal, ordinal, interval, or ratio scale are factors that determine which statistical procedure to apply.

P29 Type of Measurement Scale.

An example

• If your grade on an essay exam is based on the number of correct statements you include, then a ratio scale is involved;
• If it is based on how much your essay is better or worse than what the professor expected, and interval scale is involved;
• If it indicates that yours was relatively one of the best or worst essays in the class, this is an ordinal scale(order, as is pass/fail, which is dichotomous);
• If it is based on the last digit of your ID number, then a nominal scale is involved.
• If you can receive one grade or another, but nothing in between, it involves a discrete scale;
• If fraction are possible, it involves a continous scale.