Studies are often done by pharmaceutical companies to determine the effectiveness of a treatment program. Suppose that a new AIDS antibody drug is currently under study. It is given to patients once the AIDS symptoms have revealed themselves. Of interest is the average (mean) length of time in months patients live once they start the treatment. Two researchers each follow a different set of 40 patients with AIDS from the start of treatment until their deaths. The following data (in months) are collected.

Researcher A:

3; 4; 11; 15; 16; 17; 22; 44; 37; 16; 14; 24; 25; 15; 26; 27; 33; 29; 35; 44; 13; 21; 22; 10; 12; 8; 40; 32; 26; 27; 31; 34; 29; 17; 8; 24; 18; 47; 33; 34

Researcher B:

3; 14; 11; 5; 16; 17; 28; 41; 31; 18; 14; 14; 26; 25; 21; 22; 31; 2; 35; 44; 23; 21; 21; 16; 12; 18; 41; 22; 16; 25; 33; 34; 29; 13; 18; 24; 23; 42; 33; 29

Determine what the key terms refer to in the example for Researcher A.

variable

The variable is usually denoted by the capital letter X or Y in statistics and refers to the characteristic or measurement that may be determined for each member of the population. A numerical or categorical variable can be used. The numerical variable takes numbers as its values, such as student weight in pounds, but the categorical variable assigns categories, such as student gender, which can be classified as male or female.

For Researcher A, we have data in the given question about the average (mean) length of time in months that AIDS patients live once they begin treatment. The data is given below as:

Researcher A:

3; 4; 11; 15; 16; 17; 22; 44; 37; 16; 14; 24; 25; 15; 26; 27; 33; 29; 35; 44; 13; 21; 22; 10; 12; 8; 40; 32; 26; 27; 31; 34; 29; 17; 8; 24; 18; 47; 33; 34

Hence, the variable for Researcher A is the length of time in months that a patient lives after starting the treatment, for the given example.

For the given example, for Researcher A, the variable is the length of time in months that a patient lives after starting the treatment.