Question

The Indiana State Police union is interested in whether the number of miles driven by each trooper is the same or different for the three different 8-hour shifts. Twenty Indiana state troopers were selected randomly selected on each of the three shifts and the number of miles that they traveled was recorded.

a) Is this an observational or an experimental study? Please explain your answer.

b) What is the population in this study?
All Indiana State Troopers
The times of the shift.
The Indiana State Police union
20 Indiana troopers in each shift.
The recorded number of miles
All police officers

c) What is the factor or treatment in this study?
The Indiana State Police union
The recorded number of miles

d) What is the outcome variable of this study?
All Indiana State Troopers
The Indiana State Police union
20 Indiana troopers in each shift.
The recorded number of miles
All police officers
The times of the shift.
All Indiana State Troopers
20 Indiana troopers in each shift.
The times of the shift.
All police officers

e) State a possible source of bias in this study. Feel free to speculate beyond the explicit statement of the question. However, nothing that is assumed can be contradicted by what is stated. Please include any assumptions that you are making.

Answer 1

(a)

This is an observational study because the researcher does not manipulate the independent variable to study its effect on dependent variable. He simply collects data on the number of miles that twenty Indiana state troopers traveled.

(b)

Correct option:

All Indiana State Troopers

(c)

Correct option:

The Indiana State Police union

(d)

Correct option:

The recorded number of miles

(e)

Possible source of bias is Confounding bias as follows:

The confounding Variable in this observational study is the road condition. If the road condition is bad, number of miles that they traveled will be less irrespective of the three different 8-hour shifts.