In each of the following data problems, there is some potential violation of one

Question

In each of the following data problems, there is some potential violation of one of the independence assumptions. State whether there is a cluster effect or serial or spatial correlation, and whether the questionable assumption is the independence within groups or the independence between groups. Also state whether there are any potential confounding variables. Researchers interested in learning the effects of speed limits on traffic accidents recorded the number of accidents per year for each of 10 consecutive years on roads in a state with speed limits of 90 km/h. The also recorded the number of accidents for the next 7 years on the same roads after the speed limit had been increased to 110 km/h. The two groups of measurements are the number of accidents per year for those years under study. Researchers interested in investigating the effect of indoor pollution on respiratory health randomly select houses in a particular city. Each house is monitored for nitrogen dioxide concentration and categorized as being either high or low on the nitrogen dioxide scale. Each member of the household is measured for respiratory health in terms of breathing capacity. The data set consists of these measures of respiratory health for all individuals from houses with low nitrogen dioxide levels and all individuals from houses with high levels.

Explanation / Answer

Solution:

a. There is serial correlation both within and between the groups because the observations are close together in time tend to be more similar than the observation collected at distant time points.

Confouding variable is the time when the observations were made.

b. There is Cluster effect between groups; members of the same household should be similar because the observations in the same subgroup tend to have similar responses than observations in different subgroups.

Confonding variable is the members of the same household seems to be similar.

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.