Hematocrit, plasma volume, and blood volume were determined for 32 newborns with

Question

Hematocrit, plasma volume, and blood volume were determined for 32 newborns with the disease. Using the actual data, regression lines were created to describe the relationship between (1) hematocrit and plasma volume and (2) hematocrit and blood volume. The regression equations are the following:

Plasma volume = 70.3 – 0.39 x hematocrit

Blood volume = 60.8 + 0.79 x hematocrit

Is the association between hematocrit and plasma volume:

Directly associated

Inversely associated

Is the association between hematocrit and blood volume:

Directly associated

Inversely associated

Changing hematocrit levels by 1 unit produces greater per unit changes in which of the following:

Plasma volume

Blood volume

The regression equations above are examples of what types of regressions:

Simple linear regression

Multiple linear regression

Simple logistic regression

Multiple logistic regression

Smoking is a confounder in the relationship between hematocrit and blood volume. If we wanted to adjust for smoking as a confounder only, we could do which of the following:

Include it as a variable in the regression equation

Create an interaction term (smoking X hematocrit) and include it in the regression equation

Stratify the data into 2 groups: smokers vs. nonsmokers

A or C

Explanation / Answer

Answer

Plasma volume = 70.3 – 0.39 x hematocrit

Blood volume = 60.8 + 0.79 x hematocrit

(A) association between hematocrit and plasma volume is directly associated because every 1 unit increase in hematocrit is resulting in 0.39 unit decrease in Plasma volume. So, it is directly associated.

For inverse relationship, Plasma volume must have an equation where we have hematocrit in denominator, so it is directly related

(B) association between hematocrit and blood volume is directly associated because every 1 unit increase in hematocrit is resulting in 0.79 unit increase in blood volume. So, it is directly associated.

For inverse relationship, blood volume must have an equation where we have hematocrit in denominator, so it is directly related

(C) Equation one has negative slope value of 0.39 and equation second has positive slope value of 0.79, i.e. Plasma volume decreases 0.39 units and blood volume increases 0.79 unit with every 1 unit increase in hematocrit

so, blood volume is increase as compared to plasma volume because +0.79 is greater than -0.39

Answer is Blood volume

(D) The given regression equations are example of simple linear regression because both equations having only single dependent variable and one independent variable

These equations are not Mulitple linear regression because it is not having multiple independent variables

These equations are niether simple logistic regression nor multiple logistic regression because logistic regression has exponential function which is not present in any one of these two equations.

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