Hello, would you mind answering this question? I appreciate your help! :) (Stati

Question

Hello, would you mind answering this question?

I appreciate your help! :)

(Statistics)

* In each of the following data problems, there is some potential violation of one of the independence assumptions.

i. 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.

ii. Also state whether there are any potential confounding variables.

a. 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.

b. 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 orlow 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.

Thank you very much!

Explanation / Answer

a. Serial correlation both within and between groups. Confounding variable is the time at which observations were made.

b. Cluster effect between groups; members of the same household should be similar.

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