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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%) |
|
:
|
|
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2. Native born |
163 (85%) |
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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?