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1. A couple of years ago a data set was obtained (called ICUAdmissions) that included information for 200 patients admitted to the Intensive care Unit at a major Boston hospital. Here is a list of the variables that were recorded.

 

ID	Patient ID number
Status	Patient status; 0 = lived or 1 = died
Age	Patient’s age (in years)
Sex	0 = male or 1 = female
Race	Patient’s race:1 = white, 2 = black, or 3 = other
Service	Type of service: 0 = medical or 1 = surgical
Cancer	Is cancer involved? 0 = no or 1 = yes
Renal	Is chronic renal failure involved? 0 = no or 1 = yes
Infection	Is infection involved? 0 = no or 1 = yes
CPR	Patient received CPR prior to admission? 0 = no or 1 = yes
Systolic	Systolic blood pressure (in mm Hg)
HeartRate	Pulse rate (beats per minute)
Previous	Previous admission to ICU within 6 months? 0 = no or 1 = yes
Type	Admission type: 0 = elective or 1 = emergency
Fracture	Fractured bone involved? 0 = no or 1 = yes
PO2	Partial oxygen level from blood gases under 60? 0 = no or 1 = yes
PH	pH from blood gas under 7.25? 0 = no or 1 = yes
PCO2	Partial carbon dioxide level from blood gas over 45? 0 = no or 1 = yes
Bicarbonate	Bicarbonate from blood gas under 18? 0 = no or 1 = yes
Creatinine	Creatinine from blood gas over 2.0? 0 = no or 1 = yes
Consciousness	Level: 0 = conscious, 1 = deep stupor, or 2 = coma

 

(a) What is the individual in this case?

 

(b) Which of these variables are quantitative?

 

(c) Which of the variables are qualitative/categorical and ordinal?

 

(d) Suppose we were interested in the relationship between the two variables Status and Race. Which of these two variables is the response and which one is the explanatory?

 

(f) Suppose we were interested in the relationship between the two variables Service and Previous. Which of these two variables is the response and which one is the explanatory?

 

 

2. Determine whether the following variables are qualitative or quantitative. Where you think the variable is qualitative, indicate whether it is nominal or ordinal.

 

(a) Whether or not a respondent drinks alcohol.

 

(b) A patient’s temperature (in degrees F)  

 

(c) A respondent’s zip code  

 

(d) Number of days during the past week that a student had at least one drink.

 

(e) A mid-west college grades students using the following system; Excellent, Entirely Satisfactory, Satisfactory, and Unsatisfactory.  

 

 

3. As part of a report that appeared in the New England Journal of Medicine, the authors included a table showing some demographic characteristics of the patients included in their research. Here is an extract from the table.

 

Characteristic	Number (%)
:
1. Hospitalized in past year	25 (13%)
:
2. Native born :	163 (85%)

 

Last semester, I asked the students in my statistics class to identify the two variables shown in this table and to indicate what type of variable each was. Most of the students claimed they were both qualitative, nominal variables.

 

(a) Identify the two variables represented in this table.

 

(b) How can variable number 1, for example, be qualitative if there is a perfectly real and plausible number (25) associated with it?